AceShowbiz -

Although her sexy image has landed her a job as Calvin Klein's underwear model, Megan Fox is still insecure about her body. In a new interview with W magazine, the "Transformers" babe said, "My main weakness is nerves. I have no confidence, and because of that I'm always second-guessing myself."

She also doubts her image when wearing only skivvies, saying "There are some women you could put in underwear and photograph them, and it looks really classy and it doesn't necessarily provoke a pinup image." Referring to curvy women in the '40s, she added, "But with me, it does, immediately. As soon as I'm in underwear, I'm a Vargas girl."

Another interesting fact that she revealed about her is maternal instinct. "No one believes me when I talk about this, but I'm really maternal," she said but added later, "I worry that because I've always wanted [kids] so much, as the world goes sometimes, I won't be able to have them, even though I would be able to provide them with such an amazing environment."

The March issue of W will hit the newsstands this week. Megan also talked about why she doesn't have many friends in the industry and why she is intimidated by fashion.