Hi, Thank you very much for your questions; although it is quite difficult for me to give you a precise opinion here without being able to examine you, but I would try to provide you some relevant information about your shoulder pain. Your symptoms could be suggestive of either some nerve injury or a pressure on the nerve due to the muscle spasms due to fibre neuropathy. Another possibility in your case could be damaged the soft-tissues such as muscles and ligaments if you are over-doing any shoulder exercises or lifting heavy weights. Since you have persistent pain, I would recommend you to see a neurologist who can evaluate the details of your case and could better determine the insight of your situation. In addition, it will be best if you would also visit a physiotherapist to let him/her assess your back and shoulders. Hope this helps.