when the foreskin of my penis is pulled down, i have noticed abnormal skin on the underside of the head of my penis. the skin has very small unusual grooves around the circumference of it, like it has been slightly ripped all around it. the grooves are painless and i have had them since i can remeber. i feel very embarrassed when my girlfriend looks at it, but she insits that its nothing to worry about. Should i be worried about it?