Hi there.
Unfortunately none of us on here can really help you. We don't know what kind of situation you are in or facing in your life that makes you feel the way you do. We can all tell you to stop and to talk to someone but clearly that is not helping you at the moment and it sounds like you are not wanting to stop either?
You are still so young and it upsets me hearing that teenages as young as you feel the need to self harm in order to make themselves feel better. Whatever problems you may have in your life at the moment, seriously take a minute to think about them. Then try to imagine where you wanna be in 10 years time and what you wanna be doing. Once you've figured out where you wanna be start setting yourself a goal and aim to be there! Every time to think about cutting just get that picture in your head! If you carry on the way you are, in ten years time you will not be happy. Depression gets harder with age and becomes harder to stop yourself from doing the things you shouldn't. You need to stop while YOUR in control of your life before the depression takes control!
Maybe try to get a new hobbie? Something you will enjoy doing and that will keep you busy? Also I would suggest volunteering work. If you have an animal shelter near to where you live, ask to help out with the animals. Working with animals gives you company that you cannot get from other people. I know you may think this sounds stupid but, if you talk to an animal that you have got close with by looking after it, if you just say EVERYTHING that's on your mind to it, you will surprised at how much better it feels when you have everything out in the open.
If you do need someone to talk to then at least you have these chats to come onto. 8 years ago when I was your age, there wasn't so much availability to all this so take advantage. One more tip I have for you, is to read a book where someone has been through self harm and has been through treatment and finally after help, have become successful. Reading the pain that others go through really helps you feel like you can connect with them!
Good luck and I wish you all the best xx