Stretch Marks

Okay so the past two years, I've had these stretch marks on my boobs, I'm only 15, and I've been told that they'll disappear soon, but it's just, they go and come back. I'm so confused, especially since I'm super super skinny, like I weigh 110. I just need to know of this is normal? And if there's a way, how can I get rid of them? Because I've literally tried everything to try and get rid of them.