Im sick of my life and everything about it?

I've liked this girl for two years and everyone knew and knows. So even still one of my pretty good friends started hooking up with her and now they're dating. They're trying to keep it secret but im not stupid. I don't know what to do anymore. I have this empty feeling inside and it won't go away, whenever i see this girl i cringe. I've cut, cried, and raged. I want to end everything. I've been backstabbed and **** on and i don't evn know what to do anymore. I feel like a pussy **** but her and i have been really good friends and now i can't stand the sight of her. Someone tell me what to do im clueless and messed up right now. I'm lost and thinking about dying. I'm not some kid that doesn't have a life and unsocial either...this is just getting to me and its under my god damn skin. Help me