So, are stretch marks normal on a teenager cause the other day I was in ya know booty shorts being the positive body bitch I am and my dad yells out to me "yuh have stretch marks you need to start exercising" and like I've never had a problem about my stretch marks before until he called me out cause I thought it was normal. He said when he was my age and other girls my age didn't have stretch marks so uh- yea are stretch marks normal??