He wont keep his hands off me(15yrs old) i feel so violated and scared?

im 15 and theres a guy at my school that ive been friends with for about 2 years, hes the typical "bad boy" i guess ud say,,he has a baby and theres been a few pregnancy scares with his other girlfriends over the last few years, he also occasionaly smokes which is gross,,,im ure typical "good girl"..virgin and all of that stuff..he asked me out last year andi said kno and we were ok..but this year at school he wont keep his hands off me and its really annoying. he messages me on myspace callin me baby and lil mamma and stuff like that. ive told him to leave me along and get his hands off me but he dosent listen..and he gets mad at me if i dont talk to him. yesterday at the homecoming pep rally he kept rubbign my sholders and puttng his hands on my waist and when he asked me if i was going to the game i said no, and he said if i didnt go he was going to tell everyone that i was a slut and stuff..and i still said i wasnt goin to go so he told the guy that he knows i like that im a slut and all of this stuff that isnt true. im pretty scared..what can i do?