What's a good way for a 15yr old to get rid of stretch marks?

Hi I posted this before but it had a typo! :) I'm only 15yrs.,94lbs and 4'10 I've never been over 100lbs and I was always small as a child. I work out enough I love to being fit and stuff, But I have stretch marks on my calf's and thighs... I feel embarred to show my legs because I'm in High school and I'm young. I don't want my legs to look like I'm 30yrs.old I just want a treatment that not expensive and that will work! :) Thanks!