I am not a medical professional so I can't give you much specific advice, but I can relate a bit of my story. Sadly, your story and mine have some common threads, but since you are younger you may be in a better position to get well.

I am 29, with a wide array of upper body problems including thoracic outlet syndrome, cubital tunnel syndrome (probably related), pain in my neck and scapula, and intermittent pain in my lower back and right glute. But the problems started when I was 17 and doing a lot of, wait for it, weightlifting without a proper instructor.

Like I said I'm not a professional, so I only feel comfortable giving general advice. How is your flexibility? How is your muscle balance? Posture? Do you breathe correctly (into your diaphragm instead of into your chest)? Have you seen a skilled physical therapist or other professional bodyworker who could assess some of these things? If you haven't, I recommend it. I also recommend sticking with it until you find someone who is highly skilled, analytical, and willing to listen. I had a lot of early diagnoses when I was your age that basically went like this: "You have tendinitis, you're young, it will clear up." It only got worse. Had I seen the right people 8 or 9 years ago, I might be in much better shape now.