Any tips or products for my stretch marks please?

Hii. So i am a 13 year old female and i have stretch marks ): they kinda just started to develop last year in 2010. There redish purpelish. I am really embarresed about them. I have really pretty legs (so what people have told me) but, i dont like my stretch marks! Because of them,i dont like to wear shorts or capries. But,because of the weather,i have to wear them to stay cool. Also,do you think i am to young to be developing stretch marks? And what causes them? Any tips,products as well as help will be greatly appreciated please.