hey, I'm nearly 17 now and have stopped hurting myself for a good 6 months or so, well badly at least. I never was that bad but possibly have bipolar and get incredibly depressed, sometimes for no reason at all. anyway i hope my advice helps someone else, it's helped me a lot:
to be honest i know its not advisable by i try and stop without a doctor.. can cause more problems than it's worth. keep yourself really busy especially at night when theres less to distract yourself with. talk to someone close or someone you barely know as they wont judge and will hopefully try and help. try and determine what the problem is and work on fixing them. find things worth working towards and work towards them. reward yourself etc. hope this helps