Sore legs more upper part and mainly the back part of my leg and sore butt. It hurts when I try to sit down. I barely exercise. See a doctor?

Sciatica. Teenage female with posterior and buttock pain describes symptoms compatible with sciatica. An Osteopath might be best person to diagnose; with concern for pelvic girdle disorder, pyriformis syndrome, lumbar disorder etc. Review of the Brighton Criteria might discover Joint Hypermobility Syndrome, which is common and which can be associated with these symptoms.