02/12/2008 at 01:00 PM EST
Although she routinely graces fashion magazine covers, Reese Witherspoon
has her share of insecurities – and never more so than when she's photographed in a bathing suit.
"I hate that the paparazzi takes my picture when I'm on vacation," she tells Extra.
"Oh, my god, did they see my butt? I hope they did not see my butt."
Witherspoon, 31, who costars with Christina Ricci, 28, in Penelope
– about a woman (Ricci) with a pig-like nose – says she faced challenges with her looks starting in childhood.
"I wore giant Coke-bottled glasses as a kid, so I was four eyes," she tells Entertainment Tonight.
"Because I was short, I was the last one to be developed – which is a horrible thing to be as a girl. It taught me so much. I never could make the sports teams. So I always had to be funny if I was going to be anybody's friend or get any attention."
But, she adds, "These experiences are very formative. It's great to have to struggle in some ways. You learn this later. ... It really makes you who you are."