I’m a 13 year old girl and I’m 5’10. I have these red, purple lines on the inner of my  thighs that look like a dog just scratched me. I read comments and I do sit at school but I play basketball and softball and I get told I have no fat on my body. So I have no idea what this is. I never wear jeans mostly leggings so my pants aren’t to tight on me. Anyone have any idea what this could be