I have it too. My ex just used to tell me off for it but I think he knew it had a purpose. I just don't know what it is. It is worse when I am stressed. It's been really bad today. I have no one in my life now so I don't care but I do try to hide the scabs on my face with make up. My chest doesn't matter really. It isn't healthy but if it helps then I don't see why I should stop. I have no motivation to so I know I won't and never will now.