How to handle bullies?

Well, I am being bullied...there is this gang of guys that for some unknown reason likes to terrorize me. Well, just the other day, as I was walking through the halls...one of them grabs me and shoves me in my locker. I was in there for a whole half hour before someone heard my cries for help. And about a week before that...I was grabbed by my suspenders and hung on a coat rack in chemistry. Ok...well..that's not all, they are always giving me these evil looks whenever I p them and yesterday the leader of the gang was taunting me and telling me all these horrible things he is gonna do to Laura when I'm no where around to help...its driving me crazy, I couldn't sleep last night..please help me. I don't know how much more I can take.