There is a possibility that it could be your girlfriends p juice, you should know after you shower, If it comes off and it don't occur afterwards than your okay but if it comes bk and continues to peel, I would def. Go to the doc & put a moisturizer on your p.

Sweetie... not to be gross, but it's not skin. When girls get turned on they excrete juices and they dry up during sex, so what you're pulling off is dried up juice.