Why can't I stop!

I can't seem to stop picking. I have a scab on my wrist under my pinky finger. I have tried everything i can think of. Banaids, armwarmers, rubberbands, the horror stories, rubbing alcohol, and hydrogren peroxide. I am in college and so there is a TON of stress and I fidget and there on my wrist is a nice scab. If I accidentally touch it, rub something aganst it or whatever, I think about it and then 'BAM' then I start picking.