It sounds weird but you can be addicted to cutting. I know some people who find the adrenaline rush that stems from the injury addictive. The point is it's very difficult to stop those thoughts or desires without help. Sounds like home life is pretty rough, and if your family isn't willing to help you should seek outside help. I really think counseling may help you. School counselors can be very frustrating, but as you're under 16 that may be one of your only options unless your parents get involved. Your school should also have a teen help line with someone available 24 hours a day to talk to- someone who is your age. Please don't do anything rash. Life can be hard sometimes, but it's never worth ending.
I am sorry to hear about all that you are going through and I strongly urge you to reach out and ask for help. Please talk to a trusted adult(a parent, teacher, neighbor, school nurse, coach, school counselor, or someone else) about all that is going on. You really need to get help before it does get worse. If you are unsure of who to talk to, try talking to your school nurse. They are required by their profession/job to keep what you tell them private, just like doctors have to, so don't be afraid to talk to one of them for help. I know the teen years are rough, so please don't try to go through it on your own. If you ever want to talk, come on here. There are many listening ears who would love to talk with you and make sure you are ok. Please talk to someone about this and take care.