So a while back I've began having these weird looking lines on my skin. It's in only this area on my right arm(on the muscles) and on both sides of my legs between the pubic hair area. Should I be concerned? I'm 17 years old, 6 feet and 175lbs so I'm not too terribly obese or old(I'm saying this because obesity or age might have something to do with it). The marks don't hurt at all but don't feel flat, like I can feels slight bumps where the marks are.