I am doubtful about the skin of my penis. When my penis is not erect the skin completely slips back without any problem. But when erect the the skin does not shift back completely. That day i tried to had sex with my gf, the penis was erect and when penetrated inside, the skin slipped back and i had a severe pain(expected... but not this much pain) then i check the skin it had got a small cut/slit/torn skin because of penetration. We both were having sex for first time(without condom). Is this natural for males in first time? Or is the skin abnormal??