driving me crazy...

i know everyone has thoughts at one point or another of suicide...and alot of people try to carry out those thoughts....but what do you do when those thoughts flood your head like crazy? what do you do when you just sit there like in school and all you can think about is suicide...how do i shake those thoughts? the other night i tried to commit suicide again...i've done it a couple of times but all i end up doing is passing out or something.
i dont know what keeps me here and what keeps me going...but all the time my head is full of thoughts about being dead and killing myself. can someone please help me get over this? these thoughts are making me go insane...so please help if you can...