Stretch marks?

Madd
Hey everyone. So I'm 14 (turning 15 ) and I've got stretch marks on my bum and thighs and I was just wondering if this is normal and if so how can I remove/reduce them. I've tried using bio oil all ready but that hasn't helped and for a while I thought if I was skinnier I wouldn't get them so I started eating healthier and exercising but while my size did reduce a bit the marks stayed the same. So any other ideas?