Why do people stare at me?

I'm 12 years old and it's when I wear something certain like a plain top or something. Now I only wear usually one top because that's the only top that people don't look at me in... When I'm in the car, foreign guys and young girls look at me and then look away and look like they're talking. Some smile, but others look at me like I'm a freak. I'm too scared to go shopping, because I'm worried that everyone will look at me :( am I paranoid? I don't think I'm drop dead gorgeous and I don't think they're jealous. Help :/