I self injure... help please?!

first thing first, you should know why'd you did that.
then you should solve that problem.
if it doesn't works, you should thinking when you wanna cutting yourself, thinking like, what if you suddenly die if you keep cut yourself, or like, thinking about something you're afraid of, if you keep cutting yourself.
if it doesn't works, if you wanna cut yourself, remember about the one you love, how if you die and leave that person..
give that new pocket knife to your friend, and don't go to any shop that sells it. if you near that shop. run away quickly, to prevent yourself enter that shop.

if it still doesn't works, if you wanna cut yourself, inhale, and exhale highly and calm yourself, if you wanna cry, go on cry, that would make you feel better.

if it doesn't works, if you wanna cut yourself, go scream, so people near you would forbid you to do that.

that's all I can think about.. I'm sorry if I couldn't give any better idea.. :/

You stated twice "I really want to stop." If you are serious, you must know by now that you cannot stop without help. Throw away your pride or whatever it is that does not want therapy. This is your only hope of stopping right now. You need therapy, and it will work for you. So, swallow hard and make a call immediately to a therapist. Do not allow your mind to play games. Do not even think about it any longer, just do it!

Take up smoking or something.

Honestly, cutting and hurting yourself isn't going to make problems any better for you, and slicing your wrists ins't going to help you in any way. It will basically just make things worse :P
Self-harm isn't a possible answer to anything, but a good way to stop is to become motivated.
Try and set some goals for yourself, maybe try to do better in school, get a job, earn some credit, ect. just simple ones that can be easily achieved, this way it will take your mind off of cutting.
OR
the next time you go to cut your own wrists, think clearly. Think and really try to come up with a reason HOW self-harm will help you, and how you may obtain tetanous, blood posioning, possibly death from blood loss, depending on how deep you cut, or any other ilness from unsterilized metal (depending on what you cut with)
Basically, just try to over come this need to cut, it will never help you, self harm just makes things worse, and first you need to help yourself, before others can. Who cares if your parents dont worry about you, after all you are hurting yourself, im sure they've tried to tell you some bit of advice but really, the way to stopping, is all up to you.
Best of luck, and hopefully this has given you some inspiration to stop,
Good luck ^_^