pulling end of nailbed away from thumbnail

I've had many tics throughout my life but this one is my most recent one. I obsessively take my thumb and pull the skin at the end of my nailbed away from the nail. Picture the coin flipping maneuver but with much more force and no coin. Sometimes I do it quickly and violently and sometimes I do it slower and hold it but still with much force. The end result is my thumbnail separates from the nailbed at the very end of the nail. This causes the white part of my thumbnail to extend proximally towards the cuticle. Ill do this until a small line of scab forms under the nail at the distal end of the nailbed. Once it reaches this point my thumb is so sore that it throbs constantly and is extremely sensitive to even the slightest touch. I can only stop when the pain is so bad that it forces me to stop. At this point the pain is usually so bad that I can feel my pulse beating in the end of my thumbnail. As bad as it hurts I seem to get some sort of sick pleasure in feeling my pulse in the wound, so much so that once it heals enough that I no longer feel my pulse in the end of my thumb, I will start the pulling again until I do enough damage to make the sensation of feeling my pulse under my thumbnail return again. It brings new meaning to the expression, "hurts so good."