stretch mark help

Hi, how long does it take for stretch marks to fade? I'm 16 and have stretch marks on the side of my thighs near my hips and on my butt. they are BRIGHT RED and will not fade, I've had them for 6 months so far and I've tried bio oil and constantly lotioning and they still won't fade. I've even went to a dermatologist and she wouldn't do anything for them. They are so embarrassing because they are so bright and none of my friends have them and I hate them, how can I get them to fade!!????