Is there anyone (a therapist, pastor, friend, family member, doctor, school counselor, heck neighbor) that you can share these thoughts with that can help you work through them?
I'm sorry that you are feeling so low at this time - but the prev. poster had a good point - even if you don't believe in Hell - NO ONE knows if life after death is really greener pastures. That thought alone keeps me here sometimes.
Also, try to remember - that at some point. Life was better. Not necessarily great. But better than now. Try to hold onto that and envision that another better time will come again. Maybe not tomorrow - but there will be better days.
I hope this helps, and again - i'm sorry to hear that you are feeling this way!