As I think we all already know, Tracey Emin was on the pill at the age of 14. It was her mother's idea: “Whatever you do don't have a baby,” she said. “It'll destroy your life.” Emin's mother, who met and had children with Emin's father while he was still married to another woman and who was unexpectedly catapulted into poverty when Tracey and her twin brother were 7, holds the opinion that: “Any woman who said giving birth didn't hurt is lying. And then when she says ‘but when I saw the baby's face it made it all worthwhile' - she's also lying.” How does Emin think having a baby affected her mother? “I think it did destroy her life. My mum wanted to be a dancer.”

Emin has never had children although she was pregnant twice in her twenties, which came as a shock considering the doctors told her the gonorrhoea infection that she'd contracted in her teens had left her infertile. Both times the pregnancies terminated in messy abortions, which exacerbated an intense period of instability and self-loathing that provoked Emin to destroy everything that she'd ever made. Much of her subsequent work is based on those experiences and one hates to think what would have happened to those feelings had she not been able to channel them into her art.

Even now she has difficulties with her moods, but for the opposite reason. She's been depressed for months pondering her life, the “children thing”, she tells me, again and again. It's getting to her. Where are they? Why doesn't she have any? Will she ever? “I'll tell you what else!” she says on the cusp of another one of the revelations that litter all her conversations and pitch her headfirst into either euphoria or a sulk, “I'm in between my periods and this is my good moment. Come next week I might come crashing down again. I just noticed that as I get older I become a real victim of my PMT, which I just hate, I really hate. It's enough that I try to plan around it.” There are a lot of people out there, art critics included, who publicly wish that Emin would just shut up about the abortions and other personal stuff such as everyone she's ever slept with, being raped at 13 and her ongoing bouts of depression: “women's issues” that makes her work victimy and therefore beyond the reach of criticism. I'm not sure what these people expect her to make her work about given that the whole point of Tracey Emin is to use herself as a subject with which she can touch the lives of others and provoke debate, but the general tenor is they think she should “Grow Up”. The tent, the £150,000 bed, the fire that destroyed the tent, the stumbling out of a Channel 4 studio halfway through a live arts programme wailing “I want to be with my friends. I'm drunk. I want to phone my mum”, they're still the things that the words Tracey Emin conjure up in most people's minds.

This annoys her because all that happened quite some time ago (1995 to 1997, except for the fire which was in 2004) and she's 45, she keeps reminding me, and if that was all she'd ever achieved in her life she wouldn't be where she is now, would she? Her appliqué work, her sewing, her sculptures, her writing, her way with words in general or the book that she's putting together, 1,000 drawings, edited down from 7,000. If you want overrated, go to an auction of contemporary Chinese art, as Emin did last year: “Some unknown Chinese artist who was about 30 was selling more than a Damien [Hirst]. It's not right! If what is happening in the art market was happening anywhere else it would be called insider dealing. It is RIFE!” She hopes that her first retrospective, at the Scottish National Gallery of Modern Art this month, will show people how her work sits in the world as an idea: “I think people will see that I really did invent some kind of language.”

I hope for her sake the Edinburgh show gets better write-ups than last year's Venice Biennale, which was panned in some quarters. The review in the Telegraph was so negative - it referred to Emin as a “phoney” who, in the age of reality TV, has conned the whole of Britain into thinking she is an artist - that Emin has not yet screwed up the courage to read it. And although perhaps Venice wasn't her best, one gets the impression that the critics who dislike her do so on personal grounds, or because they are still wrestling with the idea that they have to review her at all - a syndrome that connects all the artists formerly known as YBAs (Young British Artists), but which, in view of her range, output and the popularity of her work, especially among the young, seems to apply least of all to Emin. Then there's the fact that she is also female. Here's Brian Sewell two weeks ago: “Only men are capable of aesthetic greatness...Maybe it's something to do with bearing children.”

Emin finds it annoying when people criticise her work for being self-obsessed: “Why aren't they saying it about Picasso, Van Gogh, Egon Schiele? Picasso made work about women - all the women he had sex with! It was his women, his collection of women. Or you've got great artists such as Matisse who actually shook hands with the Nazis, hung out with the Vichy regime and painted beautiful interiors. So what do people want?”

Of course she's self-obsessed “I'm an artist and I make art about me so I have to be, it's my fuel.” She's a very loyal friend, though. “I get poorly sometimes, like a wounded thing, but I'm not self-pitying.” People don't criticise Martin Amis's personality when they're reviewing his books, she complains sullenly. Why are her critics so vitriolic and condescending? Her selfobsession bothers people only “because I'm still alive”.

She does look like a wounded thing curled up on a bean bag in the large, white airy studio off Brick Lane, East London, surrounded by sewing material and all sorts of work that she tries not to talk about because it's for her White Cube show next year. On the wall is a painting by Julian Schnabel, whom she greatly admires, and in front of us is a pot of tea and two dainty teacups freshly prepared by her assistant, Alex. When she's not showing off or fuming or morbid or on fire with sheer joy, she can be very genteel. There are certain words in her vocabulary for which she drops her guttural accent and pronounces with great care, almost primly: “superior” or “Elton and David's White Tie & Tiara ball,” (which she naturally attended). I think words, which she uses to great effect in her art, are secret markers to herself. She dropped out of school at 13. How far she's come.

Emin is half Turkish Cypriot (her father's side) and is wearing a Turkey strip before the Euro Turkey-Germany football match tonight, over a skirt and her bare “brilliant legs” (her words), the outfit is complemented by half a dozen pieces of gold jewellery and the wonky smile that makes her look ridiculous, friendly, mongrel-like, warm, sexy, philosophical, kittenish, adolescent, picked-on, curmudgeonly or unhinged, depending on what's going on inside her head. She's 45, she says again. She'd like to lose about 10lb, but she's ditched personal trainers because they make her stroppy. Instead she swims. She's “mega healthy!” - gave up spirits in 1999, gave up cigarettes in 2003. “I'm a Royal Academician, I've got three honorary PhDs, what else have I got?” She's no longer got much of a temper. You're less likely to get your head bitten off if she disagrees with something you say. She can be “defensive”, but she's not the Mad Tracey of the late 1990s, although her small child's voice still inspires a kind of knee-jerk sympathy that I suspect can make some people feel manipulated.

One thing that astonishes her is how much she has changed recently. She can't believe she's the same person who told Jeremy Paxman in 1997 that if she were in charge of Britain she would introduce 24-hour drinking. I asked her what would be on her wish list now and she comes out with a whole roll of sensible suggestions such as more cycling routes and tennis courts, better schools and never having said “yes” to the Olympics. She's annoyed that despite all the taxes she pays, the quality of life in Britain is so bad; that it can be dangerous to walk down the street at night.

She first noticed this change about two years ago and it's been at the root of all her blackest moods ever since. When she was younger she made a pact with herself to have her first baby at 40, once she had £1 million in the bank and had passed her driving test (“If you've ever been brought up poor, without food, without heating, without plimsolls, with holes in things, with no Christmas presents or Christmas, you do not ever want to have children to be in that situation.”) So now she's passed her test, has a property empire of sorts - bought a place for her mother - but still no kids. In an interview last year it looked as though she'd accepted this state of affairs, but she seems wobblier now: “A few months ago I got very scared about the idea of dying alone, getting old alone because not many people do it - they have families.” To an extent it's her vaulting ambition that gets in the way. But there's also the problem of Emin's boyfriends, who always already have children. She split up with the artist Matt Collishaw in 2003 after almost six years together during which she claims he was wildly unfaithful.

“When we first got together when I was 32 I said to him ‘when I'm 40 I will want to have a baby'. And then he left me when I was 39!” Their break-up can't have been insurmountably acrimonious seeing as she included him in the room she curated at the Royal Academy's summer exhibition this year and she says that in a funny way he did her a favour. “Every day I was with him I was afraid that he would leave me so when he left it was a relief.” Nevertheless it must have hurt her feelings. “Yeah! Because every art gallery wants my stuff and every f****ing party wants me to be there.” She concedes that she can be hard to live with, the ego of an artist is pretty phenomenal. “Maybe men think one of me is enough, they don't want to take any more on.” Now she's going out with Scott, a photographer who also has kids. Has she written off the prospect of having children at all? “Every day I'm writing it off. I'm adjusting to not having them. I knew it would do my head in around the time...And also I got p***ed off because I'm quite a good woman so I was thinking, ‘but I'm obviously not good enough to have someone's children'. It's pretty irritating. Never have been. No one's ever wanted me to.”

It was her birthday earlier this month and she celebrated with a dinner for lots of friends - in the old days it would be 48-hour parties, the stuff of legends. It would physically kill her to do that now. Things are different. Just last night she was angrily thinking about the loss of Angus Fairhurst, another one of the original YBAs. He committed suicide in March aged 41: “Things aren't going to be the same again because Angus isn't here. It's funny, Angus crowned the end of an era.”

The future is freaking her out and even the present she's finding hard to cope with. She always thought the brilliant thing about not having kids “is that you can do what the f*** you like, but I don't want to do what the f*** I like. I can do anything. I can travel around the world, I can stay up all night drinking, I don't have to answer to anyone. But I don't want to be like that anyway.” For the first time in her life she's bored when she goes out, would rather be at home reading a book. “I do all the charity work and, sometimes I question the whole big scheme of things. How does it all work? What's it all for? If I was a grandmother I'd have this other kind of arc where things go but I don't have an arc. The only thing I have is me.”

And her art. As a student at the Royal College of Art she wanted to make paintings that would be hung in prisons and court houses and hospitals, never in people's houses. The point is to open a dialogue. She was pleased with the reaction to work she made recently in Folkestone concerning teenage pregnancy - bronze casts of discarded baby clothes - because she felt it started a debate, statistics on teenager girls having abortions were dug up by the papers the following week which she feels sure isn't a coincidence. “It makes me feel more useful because at least I've got something moving.” It always seems to me that women in particular like her work because it gives them permission to talk about their own experiences.

She's made another pact with herself, to adopt once she's 50, but I don't get the sense that it makes the prospect of having none of her own any easier. And she's frightened in case the authorities won't let her. If she plays her cards right as a godmother at least she'll have a younger generation in her life, “so it's not all cut away from me completely”. But the way she says it she makes it sound like a consolation prize.

What about sex, one of the grand themes in her life and her work. I wonder whether there are fears about her own sexuality loitering at the back of all these thoughts about ageing. Of course she's been obsessing about it. “A lot of women once they've passed 55, say, or younger, they're not sexy any more. I'm sorry, they're not! I've gone over it a million times in my head, all right. They're just...it's gone. It kind of floats away, it kind of goes somewhere behind them. It's not like they haven't got it any more, it's like they cast it away almost like the sex shell drops off of them and they become something else. And I've noticed this a lot and I'm frightened of that because I haven't got children.”

Sex really does get her up in the morning and the thought that it might desert her, that it's not going to be there, turns into an idea rather than a reality, “is a really interesting thing for women”, she says, by which I infer terrifying. “And a lot of feminists and a lot of women would really shout me down for that. But I know what I'm saying is true.” This is what she meant in her photographic self-portrait, I've Got it All, which shows Emin giving birth to a pile of banknotes: “I was saying I haven't actually got anything, that's it. There's no other level of fecundity that's coming out of me except this material one. The raw stuff, the thing that propels people through life, that's not happening to me.”

Today started badly. She slept terribly and spent the morning making a fuss of Docket, her cat of eight years who is ill. She fears that the love she has lavished on him will become a “festering thing” if he dies.

Then she spent an hour deciding whether to have breakfast first in the kitchen and then a shower, or a shower first, then breakfast on the roof of her beautiful home. “There's a lot of men that would give up everything to be in my position, to have the success that I have. It's like a Faustian pact. They'd swap their wife, their children, everything. They're so desperate for that success. And I'm not like that. My art is just like, kind of, it's what I do and the success of it is on top of it and really brilliant, but there's this other side of me that I don't know whether I'll ever know whether I'll be able to explore, which will always just have to be suppressed and pushed down.”

I don't think Tracey Emin is capable of suppressing anything and her thoughts on all these subjects will no doubt bubble to the surface and enrich her art in the future: how avoiding having a baby that might have destroyed her life, nevertheless destroyed her life. And how childlessness in later life casts its own shadow. At least doing art, she says, is still incredibly fulfilling and a goofy besotted smile spreads across her face. “I've never done bungee jumping or jumped out of an airplane, but I think it might be comparable to that.” Female artists traditionally peak in their sixties. “It's quite exciting actually.”

Tracey Emin 20 Years, Scottish National Gallery of Modern Art, Edinburgh, August 2 to November 9

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