Sweetie. Our skin does weird things. We have hair follicles in that area too. It doesn't hurt, you've had your mom look at it and she feels it's okay, so try to not analyze it so much. Masturbation doesn't cause issues. You may be scratching when it itches (we all get an itch there sometimes) and then when urine hits it, it stings. In all honesty, you do not describe anything I would be worried about. good luck