I Agree with holyohio it deffinately sounds like depression, dont worry alot of ppl go through it, and alot of ppl do give in to the thoughts of cutting and such, which is not very smart at all, but i cant say too much about that seeing as i used to do it..
uhmm...again i think holy is right you need to talk to someone about this, or keep a journal or such, i know writing always made me feel better, sorta..
umm i dont really know what else to say about this..sorry