I scratch in my sleep, to the point where I bleed,?

and I have been doing this ever since I can remember, probably since I was about 10 or so, so for about the past 11 or 12 years. I scratch my neck and face badly, and on my back, chest, neck, arms and shoulders are usually the worse of the scratches, they usually swell up from being scratched so hard, and they bleed, they almost look like cat stratches I guess, and I dont have any pets, and on top of it I have pretty much no nails at all, I bite them down pretty short.. Its not my bath soap, or detergent, I have changed it all multiple times, and I only scratch like this in my sleep, does anyone have this problem, orr know someone who does