Sounds like your situation is very complex. As a start it could be a good idea if you find a way through which you can externalize your emotions instead of self harm. Catharsis helps, talking with others, journaling, art, music etc. find what you are interested it. But I dont think you can sort this out alone, telling your parents would always be a good idea. You could contact a school psychologist, confidentiality depends of if you are a minor or not, so I would advise you to read some about it, if you dont want the therapist to contact your parents. Mental health isnt as stigmatized nowadays, so if your parents are understanding, please just tell them that you are struggling and in need of psychological help.
#how do I stop??
cinder chasm
Learning to let go through meditation could help you out if you always want to be perfect.