Why do I always get bullied?

I am in middle school and there is this group of "popular" people. They are always making fun of me! For examples 1. One time I was reading in the library and they said look a freak in her natural habitat. 2. One time there was this boy that actually liked me for who I was. Then a guy from the popular group went up to him and said How could you like a ugly monster like her. I don't consider myself ugly and most people don't either. I have soft blue eyes, smooth pale skin, and light brown hair. I just don"t get it, they always try to make me feel bad. My confidence level is really low, and everyday when I get home from school I lock myself in my bedroom and cry. I think it is because I am smart, I make all "A"s and am in GT (an extra class) But what is wrong with smart people? Really, what is wrong with us? I just don't understand.