I can actually relate to that. I was diagnosed with genetically inherited depression at a rather early age, and I've had to deal with this kind of situation before. Never got into self-mutilation, but I've had those same thoughts. Going to sleep one night and praying to not wake up. Hoping for hopelessness to end.

I assume that this is not a work of fiction, and that, in fact, it is a representation of your actual life. Talk to your parents or another adult figure about therapy or medication. I know exactly what it feels like to think those things, and it will never go away on its own. Seek help. It's the most important and crucial thing that you could ever do for yourself.