Posture and upper back pain

Would an MRI or an X-ray be helpful for my upper back? I injured myself boxing over two years ago. It was diagnosed as a thoracic sprain, though it has never healed properly. The pain and minor numbness/tingling occurs in the muscle between my shoulder blades and well as in the muscle below the shoulder blades. I cannot get an accurate diagnosis. My doctor thinks its muscular and my physical therapist thought it may have been a disc problem, but now thinks it may be Tendinosis. I realize asking via a website will not lead to a accurate diagnosis, but I still would like to ask and perhaps explore other avenues of treatment. Does my weight of 380 lbs play a significant role in the pain or recovery?