Advice?

So I'm 13 and I have stretch marks on my hips and thighs and they make me so self conscious. I'm not overweight but I have big hips because I horseride. I knew about my stretch marks and I was fine with them before my mam caught a glimpse of them and pointed them out ever since they have made me feel absolutely shit about myself and how I look. Can you all give me some advice on how to get ride of my stretch marks