07/12/2011 at 12:15 PM EDT
, who is now expecting her second child,
says she never quite lost all the baby weight from her first.
"I can't ever get down to the weight I was before I had Honor
," the actress, 30, tells the August issue of Allure
"My body's just different. The jeans just sort of zip up differently, and things hang differently. It's a miracle what happens, but you definitely are different afterward. Unless you're Gisele
But having a baby had another unexpected effect on Alba: It helped her get more in touch with her own sexuality.
"I was quite shy with it," says Alba, who stars in Spy Kids: All the Time in the World
, out Aug. 19. "It wasn't something I embraced until I had my daughter. I saw how incredible and amazing it is to be a woman and to be able to create a life. There's a reason why certain areas of the body are desirable – because it all leads to reproduction."
She adds: "There's a science behind it all. It's not just to sell whatever you're selling on a billboard or a magazine or a movie."
The one part of being pregnant that Alba could do without? The scrutiny from the press about her changing body.
"My publicist said the other day, 'You can't just be going to the grocery store – you have to be 'flaunting your baby bump,' " she says. "You're pregnant. Your stomach is not going to be flat. You're not 'flaunting' it; you're just walking to the store or across a parking lot."