I am the same way. I don't know what to do about it though. Sorry.

you just have to realize that its not going to fix your problem. easier said than done, i know. maybe you need to sit your parents down and tell them you have a problem and that you need help. they probably think it is just a phase or that you want attention.

Let's look at some of the things that get you angry right now. We call them "triggers". Need to understand some of the reason why you may cut. Built up anger inside that you can not let out. Needing to thrash out at someone and take it out on yourself? How you see yourself........Are you comfortable with your looks, your weight? How bout your home life. Parents getting to be unlivable?
You have to look at all the deciding factors here and start sharing those feeling with the people the people you want to lash out at and meet it face to face with a non-agressive attitude.

Give it a try.

Perhaps talking to a therapist would help you sort out some the reasons why you are in so much pain. That may help you find other outlets instead of self harm. You need to value yourself enough to not hurt yourself. A therapist can help you find yourself and give you tools to use instead of self harm.