why so many damn stretch marks on my side/legs

why the hell am I starting to become covered in stretch marks!!!! They look discusting, I'm 18 and have these discusting things. I haven't put on weight to cause this. I don't mean to be rude to anyone that has them cause I'm sure they beutiful. But I hate them on my self. Makes me look fat and horrible and self conscious. I literally have them on the back of my thighs/legs/knees. Inside of my thighs and up my sides . Out of nowhere How can I get rid of them/cover them. I will get them lasered of if needs be. And how can I prevent them. I just want to cry. 1 more thing to make me more discusting :(