Are you parents supportive or not really? I guess not really. I guess your stutter is very severe, in this case I understand that you dont want to "talk" to you parents about it or "talk" to a psychologist. The next time, instead of self harming, try to write on you PC. Write how you feel and that you need help. When it is finished, print it out or send it to your parents. They are responsible for you and also for your happiness and well being at this age. Really try it, you have nothing to loose but it can help you.