Why do we get stretch marks, I'm not fat I'm a healthy size 10 , but I don't understand I have them on my bum my legs back of my knees my theighs and boobs?

At one time in your life you were probably little heavier and lost it, maybe a couple of times. Therefore stretch marks. There are lotions you can by that erradicate them somehwhat.

Tick

People have different skin elasticity. Try daily applications of coco butter to help prevent additional stretch marks. Be aware there may be a genetic component