It really stinks when the adults in your life, who are the ones who are supposed to act grown-up and responsible, and to keep you safe, are the ones who hurt you by acting irresponsible, neglectful and mean.
It's also horrible that you were being bullied in school and none of the teachers did anything to stop it.
I was in a very similar situation in middle school, so I know how you feel.
I think you should talk to your best friends about why you were acting the way you did. Hopefully they'll understand and forgive you, but even if not, talking with them will at least give you the closure of knowing you did your best to try and patch up the relationship.
Although if your best friends also bullied you after you said whatever it was, I can understand if you don't want to talk to them about it. Instead, it might be best to start fresh with new friends on a clean slate, as hard as it may be to separate yourself from those you were once close to. If your best friends did not bully you, and I am misunderstanding, please ignore this paragraph.
I definitely advise talking to someone you trust about what is going on. I also advise you to go see a counselor, therapist or psychologist, as Little Miss suggested. They are trained to help you move past a lot of the pain you are feeling, as well as to come up with strategies to make life less painful for you, and maybe eventually happier.
I hope that everything works out well for you. If you ever want to talk, feel free to post again or
PM one of the members here.