What could help me, mentally?

I'm sorry you're hurting so much emotionally. I think therapy and possibly medication would be really helpful. Since your mom isn't helping, and it seems like both she and your brother may be abusive, I strongly encourage you to talk to your school counselor because he or she may be able to help. If for some reason the counselor isn't helpful or doesn't believe you, maybe you can think of a teacher, friend's parent, religious leader, or other adult you trust enough to listen to you and help you. Also, if you feel suicidal again, you can call a free suicide hotline at any time of the day or night (1-800-273-TALK). I hope you feel better.