The upper right part of my back always hurts a lot why?

Musculoskeletal: Chronic constant pain right upper back of teenager likely muscle-tendon stress/tendonosis. Commonly at site of levator scapulae insert on superior scapula spine or rhomboid major muscle insert on medial contour of scapula. Postural station of body gives clue: tilted head, scoliosis of spine (functional or organic) & whether unilateral unstable sacroiliac joint causes either/or. See an osteopath.