Please help me - i dont know why but i want to self harm?

It is normal to feel this way. I've been there. I myself have attempted suicide 3 times, many years ago. I'm glad that I never succeeded, as I have so much now to be thankful for and happy about. If you really feel like getting out the emotinal pain, find an open field, a park, an empty parking lot, just somewhere you won't disturb anyone and get the cops called!! YELL AND SCREAM AS LOUD AS YOU CAN!!!!! It's kinda like the "yelling into a pillow", but on a much larger scale. It really does help. Don't cut yourself. This will only leave scars that will follow you. Don't break a bone intentionally. This can cause greater damage than what you were going for. It can damage nerves, puncture veins, and possibly leave you with a trail of corrctive surgeries.