While her ex Joel Madden preps for a new baby with Nicole Richie, singer Hilary Duff is delaying her own plans to start a family.

“I’m definitely not ready to get married,” Duff, 20, tells Cosmopolitan in its January issue. “I think a reason that people in this business get married young is that they feel like everything comes to them sooner in life. It’s normal to be like, ‘Okay, what’s next?’ ”

Having famously dated Good Charlotte musician Madden for 18 months ? before they broke up in November 2006 ? Duff is currently dating NHL player Mike Comrie.

On the heels of this week’s Jennifer Love Hewitt controversy about body image, Duff said that, as a scrutinized starlet, she has fretted about her weight.

“You lose some happiness when that’s all you think about,” Duff says. “There definitely was a time, about a year and a half ago, when I was pretty obsessed with my body and my weight, but I’m better not stressing about my body all the time.”

She adds, “It’s not attractive when girls get super-skinny. Guys don’t like it. Girls don’t like you as much.”

Next year, Duff will be tackling her first serious movie role, in War, Inc., costarring John Cusack. This year she spent promoting her latest CD, Dignity, which hit stores in April.