Did dr do any imaging (x ray/MRI etc) to actually verify if there are some physical issues with the shoulder or cervical spine?

If those possible issues ( tear, bursitis ,disk, arthritis etc) are ruled out, then maybe expert chiropractic? Perhaps one with a soft laser (also called low level laser or cold laser.)
Not to be confused with LED light therapy.. Laser is quicker and much better than LED therapy.

Did you do any repetitive, reaching , overhead work or desk job for years, or prior sport/injury in that area? then it could be a chronic shoulder injury...plus PD..