21 with hip, knees and shoulder pain

Patient: 1 1/2 years ago I did a half marathon and trained through hip pain. I took a 5 week break then started running again until my hip got so bad it hurt to walk, with pain on the outside of the hip focused on a single point, feels like right where my joint is. When I stretch the hip and it pops it hurts much more. Seen multiple doctors, each time a new diagnosis. I got an MRI which revealed a small tear, but one doc said he didn’t think that was the problem, rather that I have an inflamed ligament that pops over the bone when I run, which seems to make sense. Gave me a cortisone shot which helped a lot, I was able to run 10 minutes without pain (before I couldn’t run 2 steps!). Also physical therapy with ultrasounds. I began running only on flat surfaces and short distances but my hip never got better, just less bad temporarily. Still can’t run. 5 months ago my knees started hurting, particularly when I dance (I dance for 10 hours at a time sometimes, very intensively, using my whole body). I started wearing knee braces when I dance. Recently they became so bad I can’t dance, even with much better knee braces. My knees very occasionally pop causing sudden pain, they are a bit puffy/swollen, and hurt more on the insides. Also months ago, as I couldn’t run, I started swimming, until my shoulder started bothering me. It got too painful so I stopped swimming and push ups. Did not swim for 5 weeks, swam once very lightly, a few laps, afterwards I couldn’t move my shoulder. I’ve been swimming once a week, lightly, for three weeks but now it’s back to being very painful. I’ve been applying anti inflammatory cream to my hip, knees and shoulder for 1 week and powerful anti inflammatory pills, 3 a day. Starting physical therapy in a week. I also have terrible knots on the right side of my back, and according to a friend my spine is swollen. I can’t run, dance, or swim….I can’t even do freaking low impact exercise videos!!! Help what is wrong with my body, I’m only 21. Could this be systemic? Any ideas??Thanks to anyone who actually read all of that !! and has thoughts on what might be wrong…

Symptoms: Pretty thoroughly described above.
Hip is tender at the single point previously described, shoulder currently aches, knees & hip feel extra pain when I sit cross legged.