I also did this a while, but with my fingernails.
I also didn't believe it, that it's selfharming behaviour, but after I found out, I wanted to stop.
It's not easy, but it's possibly with relieving your stress.
I know it very exactly. Because I also have it.
I also thought this has nothing to do with stress and so on, but in reallity my stresslevel was chonically too high.
Autistic people can't cope with stress very well, but have chronically too much.
_________________
"I'm astounded by people who want to 'know' the universe when it's hard enough to find your way around Chinatown." - Woody Allen