Insomnia, self harm, what to do before things get worse?

I've always had trouble sleeping, ever since I could tell the time, but since I started secondary school its got so much worse. I start to worry that im not going to get to sleep and that I'll end up falling asleep at school or something, I know it sounds ridiculous. Id get worried it was really late and id start to cry myself asleep. It improved before the summer holidays but since September it got so much worse. Id have to check that my door was closed, my ipod was off, curtains were fully closed, toilet seat was down, taps were fully off etc multiple times. The whole process would take about an hour before i could atleast try and relax, then id keep getting out of bed to check things again. I did not cry however. Then about a month ago I cut myself for the first time because I couldn't sleep, it took my mind off things and helped me relax so I could sleep. I've done it 3times since and it feels good. I know its bad but I just Tell people my cat did it and they believe me. I've been doing the cutting on my wrist and only when I can't sleep. I want to Tell someone but not my parents yet, some of my mates know but they just said that I was being stupid and aren't very sympathetic about it. Any advice? I apologise its really long :)thank you :) Oh yeah, and Im 14, thanks!