By Ulrica Wihlborg
March 21, 2011 12:00 PM

Last August, Melissa McCarthy was driving down Santa Monica Boulevard in L.A. with her parents in tow when the actress suddenly had to pull over. Down the road, she spotted a billboard for her new CBS comedy Mike & Molly, and immediately “I got choked up,” says McCarthy. “It was one of those silly moments because in other sections of the world it was just a billboard. But it was a big deal to me. I’ve never been on a billboard before! It was overwhelming. We sat there in a weird gas station and I had a good little happy cry to myself.”

It’s been a long time coming for McCarthy, 40, who was once told by a manager that she’d never work in Hollywood if she didn’t lose weight. “It really hurt my feelings,” she recalls. “I understand that the odds are not as high as if I was skinny, but I still have talent. I thought, ‘I’ll show you!'” McCarthy is a woman of her word: After memorable roles as the flighty chef Sookie on Gilmore Girls and Christina Applegate’s best friend on Samantha Who?, McCarthy is a breakout star. Each week Mike & Molly draws about 13 million viewers eager to watch the evolving relationship of a couple who met at Overeaters Anonymous. McCarthy admits she was hesitant to sign on to the project at first. “I’d never done anything that touches on weight. I just don’t find it funny,” she says. “But there is a sweetness between these characters. Weight wasn’t the topic of the show. It was a slice of the pie.”

Her recent success hasn’t always been sweet. Last October a Marie Claire blog story sparked an uproar when writer Maura Kelly criticized the series, saying she would be “grossed out if I had to watch two characters with rolls and rolls of fat kissing each other.” Says McCarthy: “It was so unkind. I thought, ‘Shame on you.’ At a different point in my life, it would’ve crushed me. But it didn’t.”

She credits her strength to her parents, Sandy and Michael, who encouraged McCarthy to fuel her funny side while growing up on a farm in Plainfield, Ill. “I’d perform for my poor mother in our laundry room. I’d make up songs that were never-ending,” says McCarthy-a high school cheerleader who dreamt of appearing on Saturday Night Live. “As a teenager I went all Goth, but I wasn’t mopey enough. I would pretend to be, but I’d end up making people laugh.”

In 1996 her comedic touch led McCarthy to L.A., where she joined the comedy troupe the Groundlings and met her husband, actor and writer Ben Falcone, 37, whom she wed in 2005. But McCarthy-who admits, “I’m not afraid of a Guinness and a burger!”-knew her waistline might have harmed her chances of landing a regular gig in size-conscious Hollywood. “I would always cry to my sister Margie,” says McCarthy. (Actress Jenny McCarthy is her cousin.) “She is built like a bird. I just don’t lose weight easily.”

Luckily she didn’t have to. Her big break came in 2000 when she landed Gilmore Girls, where “weight never came up” she says. That didn’t stop McCarthy from signing up for a doctor-supervised all-liquid diet of 500 calories a day, which led her to lose 70 lbs. in four months in 2003. “I’d never do that again,” she says. “I felt starved and crazy half the time.”

The pounds later crept back on when she was pregnant with her daughter Vivian, now 3. “It was the first time I ate something and didn’t give it a second thought. If I wanted a piece of toast, I’d have one,” she says. “It felt magical.” After welcoming her second daughter, Georgette, now 1, she’s battling the postbaby weight again. “With the second one it’s not coming off as easily! I see my reflection and I’m like, ‘What’s that in my sweater? Oh my God, it’s me!’ ” says McCarthy. But instead of targeting a certain size, “I want to be healthy. I don’t have a goal weight. I’ll know when I feel good.”

To get there she works out with trainer Viveca Jensen doing Piloxing (a mix of pilates and boxing) and playing tennis. “I’m trying to do things that are fun,” she says. She’s also trying to be a good example for her girls. “I want to show them how to be healthy,” says McCarthy. “My husband and I always make a pot of vegetable soup that we puree and keep in the fridge. They don’t eat processed foods. But if my oldest daughter wants a cupcake, once in a while I’ll let her have it.”

The best lesson she’s going to teach her daughters? Don’t sweat the small stuff. “Part of being young is you think gaining 6 lbs. is the end of the world,” says McCarthy, who next stars in the comedy Bridesmaids, in theaters this May. “Being older, I’m not as hard on myself. The important things in my life-my family, my kids, my job-are so wonderful. I feel really lucky.”