I have bad strech marks on my thighs and the back of my legs:(?

Well im 15 years old and this is really annoying and embarassing! i have strech marks on my thighs and the back of my legs , they dont seem to be going away i got told to use bio oil but i havent used it yet my friend told me to use bio oil, but all i wanted to know will they ever go away?? i cant stand it, i cant wear shorts , thanks if anybody answers, xo