noone seems to understand

I've been self-harming for a few years now and my parents found out about a year back because I needed stitches... they flipped out and have decided I'm part of a self-harm ring which is crazy, I don't know anyone else who does this so where that got that from I don't know...
Anyway my girlfriend always tries to talk to me about it and she's done all this research which is fine but whenever she does talk to me she reels out these statistics and it feels like she's put in a box or something. Like he's not talking to me, Steve, but to a Repetitive Self-Harmer who etc etc etc
And she didn't used to be like this, she used to be ok but a month back she had to take me to accident and emergency and since then she's just gone wierd.
And so there's noone who understands that I can talk to...
how can I get them to change?

They're just concerned that their kid is cutting himself up, any parent would be. Try not resenting them for it and if you want them off your back stop giving them cause for concern about you, at least until you move out when you can do what you like without anyone interfering. Heres some advice: Stop harming yourself, go outside, get some sun, find a nice girl and get a blowjob. Not much else is going to change your life.