The singer-and-actress admits her body has changed since giving birth to the couple's 11-month-old son Bronx but knows the Fall Out Boy rocker still finds her attractive.
She said: "Pete isn't worried about stretch marks. He always makes me feel sexy.
"There's going to be a time when I'm way curvier, and that'll be sexy too. What defines sexy is not someone's weight. Personally I like curves... I want to look good for me. I want to feel good."
Ashlee, 25, says she gets regular exercise by carrying Bronx around all the time.
She said in an interview with Women's Health magazine: "I do Bronx Pilates! And these biceps are from holding him. He's in my arms all the time."
Ashlee also revealed being a wife and mother has "humbled" her and everything else comes second to her family.
She said: "Being married made me able to share more. Now Pete and Bronx come first. It has humbled me."