Why do guys pick on me?

At school all the guys make fun of my boobs. They tell me I have over sized boobs, They say that when I run they slap me in, the face (NOT TRUE), I can hit someone in the face with my boobs and stuff like that. This one guy said my nickname would be **** and I told him his was di*& face n he was like I have a face and a d*^&% so thanks for stating the obvious. I hate him hes the main guy that does it and also I wear slouchy berets and some people call them beanies but they're a little diffrent. They are really cute but everytime I go to the bus stop with one on these 3 boys in 6th grade (Im in 8th) talk about my hair and how ugly the hat is and they said why would she wear that to school? I just ignore it cause they don't have the b&**s to say it to my face. I try not to care but hearing and dealg with it everyday is angering and annoying. Btw I told the guy that talks about my boobs to stop.