I do this all the time, I just always figured I was the worst most self loathing attention seeking idiot until I got on this forum and noticed a couple things people have said seemed similar!
For me, I want the pain, but more than that I want the sympathy that comes with being seriously injured in a way that people can actually see. The pain I'm always feeling is invisible to people so they don't know that you always need help, a broken leg is pretty clear to everyone.