HELP PLEASE Addicted to picking at my arms?

Okay, so for pretty much as long as I can remember, I've had these bumps on my arms, shoulders, and some on my face. When I was in like the 7th grade, I picked at these bumps a couple times because it was fun to watch the white things come out, and I also felt that feeling you get when you pop a pimple, like oh thank god that one is gone. It started getting irritated so I stopped. During my first year of high school, after like the 4th person asked me why I had goose bumps on my arms when I wasn't cold, I got embarrassed and started picking at them again. It's become somewhat of an addiction and every time I see the bumps I literally can't help myself, like I HAVE to pick it, and sometimes I'll go to my bathroom to do one thing, and end up picking at my arms for like 15 minutes. Then, my arms get all red, and it looks like cuts, some bleed, and my mom asks why I do it. I don't know. I cry and cry because I don't want to look like this and I don't want these bumps. I really don't mind them so much, I just want to stop. How do I go back?