BK,
A couple of things.
Go see a Dr. that specializes in shoulders/elbows. As has been portrayed already, labrums are very, very tough to diagnose properly...even with MRI's with contrast. My son had three, two with contrast, two showed nothing, the third showed a tear. On top of that, a shoulder guy will give the best options for treatment planning.
Lifting can also be a source of aggravation of the shoulder. If it is tendinitis, complete rest is the Rx. This can be supplemented with NSaids (Naproxen, Ibuprofen, etc.) to reduce inflammation, and possibly even cortisone shots (although I have no idea about how cortisone is used in young people).