Boyfriends, babies and Ben

In her latest film, Ghosts Of Girlfriends Past, the 37-year-old stars as a single career woman nursing a broken heart after reuniting with her childhood sweetheart, only for him to dump her all over again. The film co-stars Matthew McConaughey as the cad in question: a glamour photographer who discovers how many women he's treated appallingly when he is visited by their ghosts. McConaughey's character has a great line: "Love makes you weak, dependent and fat".

"That can be true," Garner says, nodding in amused agreement. "Look at me. I'm 20lbs heavier than before. But I'm fat and happy."

Briefly wed to actor Scott Foley, whom she met on the set of TV series Felicity, she later dated her Alias co-star Michael Vartan before meeting Affleck. She was three months pregnant when the couple tied the knot four years ago in a beach ceremony on the Turks and Caicos Islands, today arriving at the wisdom that "having kids is a much bigger commitment than getting married".

Clearly valuing her privacy, Garner is evidently less at ease discussing marriage than she is talking about motherhood. "I just sound like a women's magazine whenever anyone asks me that. It's such a huge thing to talk about that I don't feel very eloquent about it. I can't remember what I was like before, so I don't know how it's changed me. It just is, obviously, the hugest thing.

"I think it's difficult for every working mother," she says. "For me, I have it easier than most. We made this movie 11 months ago and I've had all this time off, to be home, to be adjusting to pre-school, to be making dinner every night. Now I'm doing a day of work and everyone at home is like, Where are you going? What do you mean, you're working?' "Acting is a great working mom's job and I have help, although it's always complicated. When I first hear about a job, my immediate reaction is, I can't do it. I don't want to do it,' but there's a pull. I love my job. I love what I do and I think that it's a huge decision to stay at home and not have that, particularly given the flexibility that I have. But I now have to love something almost too much in order to say yes to it because I just want to hang out with my girls. I didn't anticipate that. I thought that I was much more of a careerist than that."

Having previously starred alongside her future husband twice within the space of two years, in Pearl Harbor and Daredevil, Garner is adamant that she won't be signing up again any time soon to work with Affleck. "No, no, no. It doesn't work," she says. "It never works." Garner refrains from any overt reference to her husband's foray into this realm five years ago with his then-fiancée Jennifer Lopez, when they co-starred in poorly received films Gigli and Jersey Girl. "It would just feel so incredibly weird," she says. "I couldn't do a scene with him for all the tea in China."

Starring in Ghosts Of Girlfriends Past, which essentially takes a look back at former relationships and asks the question "what if?", provided a unique opportunity for the actress to ask herself a few soul-searching questions. "Relationships are such a huge topic, aren't they? And when you break up with someone, you often feel like it could have been the right person, but there has to be several versions of a right time.

"I remember there being someone when I was really young. I was just desperate for him to want to be with me. I wasn't right for him, he wasn't right for me, and he was smart enough to see it. It's easy to just say that men are afraid of committing, but probably at a certain time in their lives every guy is like that because he shouldn't be committing - he isn't ready to or the relationship isn't right."

Garner took her time finding the one. "I've had some horrendous blind dates and also some horrendous dates with guys I had known for years, who had been friends and finally they had said, Oh, I'm going to take you out.' I do think that if you want to ask somebody out for dinner for the first time, you don't pull out your credit card and say, Wanna split it?' These situations can be so awkward."

Not that she has spent any significant period of her adult life on the dating market: "Believe me, I don't want to be on the market. It's a nightmare out there," laughs Garner.

While the paparazzi frequently capture the actress out and about with daughter Violet, it's clearly something she's not happy about. "Do you really want to talk about this?", she pleads.

"But he Affleck taught me that you cannot read that stuff in the tabloids. It's poison. It's horrible to read anything written about you. I would read the positive stuff if somebody went through it first, just to make myself feel good. But it's too dangerous because one sentence will be positive and the next is just cutting your head off, so I just stay away from all of it. We try our very, very best to stay out of that world. We try to be boring."

It's a curious attitude, although you can't know how it is until you've walked in that person's shoes. And she clearly has reason to be wary, as she goes on to reveal how she is still pursued by men, despite her very public status as wife and mother. "Men will still come up to me with pick-up lines," she says. "I find that really amazing. Oh yeah, guys do love a pregnant girl," she says, her smile masking a weariness with a situation born both out of fame and also from a natural beauty which clearly makes her more approachable than those more manicured and polished members of Hollywood's sorority.

In Ghosts Of Girlfriends Past, McConaughey benefits from the experience of getting to look back on his past romantic experiences and seeing how many hearts he has broken. Garner reckons a similar trip into the past might benefit us all. "I wish that I could go back in time and check out what the other side of a break-up was," she says. "Or make a guy go back and check out what the other side was - the devastation he has wrought. That's the thing I love about this film. I mean, who doesn't have a what-if question? You know, what if I hadn't done this or what if I had gone down that road? It's just the age-old big fat what-would-have-happened-if question.

"Who doesn't remember the first person they had those kind of feelings for? I mean, Donny Osmond? I'm still waiting for him ... And, of course, I still remember my first boyfriend. It was around ninth grade. When we first started going out together, he was shorter than me and by the time he broke up with me, eight or nine months later, he was this much taller," she says, indicating a good six inches. "Ending a relationship is never really that much fun but some ways to end it are better than others."

Garner still remembers her first kiss. She smiles. "First kiss, Matt Crittendon. He broke up with me the next day because he said I was a prude. I was 14. To this day, I don't know what he meant. My first serious relationship was when I was 15 or 16, and I dated the drummer in the school band. I played the saxophone."

In adulthood, she has had some of her own personal what-if questions answered. She has it on good authority that one of her first boyfriends has since gone on to become a successful architect.

The middle daughter of three girls, born to a chemical engineer father and an English teacher mother, Garner grew up in West Virginia with solid family values, attending the local Methodist church every Sunday. Halfway through a chemistry degree at Ohio's Denison University, she discovered a passion for acting and changed her major to drama. Moving to New York, she earned $150 a week as a theatre understudy by night, auditioning for TV parts by day. After winning roles in TV series Time Of Your Life and Felicity, she earned her first major film break starring as Ashton Kutcher's girlfriend in the forgettable Dude, Where's My Car?

But it was her role as Sydney Bristow in spy drama Alias that brought her to Hollywood's attention, and saw her eventually moving to Los Angeles to capitalise on film opportunities with roles in Catch Me If You Can, 13 Going On 30, The Kingdom and Juno.

Although she boasts Leonardo Di Caprio, Tom Hanks, Michael Douglas, Christopher Walken and Colin Farrell among her illustrious male co-stars, Garner remains refreshingly unpreoccupied with the shallow trappings of beauty and celebrity. She reluctantly had her ears pierced for the first time three years ago in order to wear $250,000 diamond earrings for the 2006 Oscars ceremony.

Possessing a quiet inner confidence, Garner clearly doesn't need the hollow acceptance that comes from attending parties and red carpet events. And while it's still a long time off, she is quite clear as to what dating advice she will impart to her young daughters.

"Respect would be a huge, huge part of that," she says. "I can't even think about it. It just makes the hair stand up on the back of my neck. So, yeah, they should demand respect. Demand it. Absolutely, you have to be a self-confident woman to demand respect from a man.

"And it doesn't hurt to learn a good right hook."

Ghosts of Girlfriends Past is released on Friday