Picking since childhood

I've been picking the skin off my thumbs since I was a child (about 5 years old). When they start to bleed, I put bandaids on them until they start to itch, then I start all over again. I've had them healed a few times but it did not last. I get a lot of emotional relief from picking them but I have no idea why. Could it have been some kind of trauma that I've blocked out or could it just be my nature to be anxious? I welcome any ideas or suggestions on this. Can't stop picking!