I've had stretch marks for a while, and I have no idea why. I was never pregnant, I'm slightly underweight for my size, and I always have been. I thought stretch marks appear if you gain weight suddenly, or got pregnant. But for me they just sort of appeared for no reason.
They are red, and really ugly. Is there any way I can get rid of them? And prevent them from happening in the future (better diet, lotion, whatever)

Thanks in advance.