Stretch marks.
I'll tell you my story about stretch marks. My first stretch marks I got in puberty, they appeared on my knees, and on my back. It went pretty well, I didn't even notice them often. Our second encounter was when I was pregnant, so I got them on my belly, and my breast It wasn't a surprise for me, as I knew my mom has them as well, and it's common to have stretch marks if somebody from your family got it too. I didn't even try to get rid of them, as I knew that stretch marks a