We are all our own worst critics. Everyone is beautiful in their own way.
It could be cause they think you're cute, maybe not. A lot of the time when you're worried about how you look you kind of exaggerate these things in your mind though and get paranoid about people looking at you even though they might not have been looking at you for any particular reason. People glance around when they walk through the mall and look at other people, it's no big deal.