I agree with roller, exercise may do more harm than good right now.
I suggest you see a sports medicine orthopedic surgeon that specializes in shoulders for the pain you are having.
That's the way to get a proper diagnosis on what is and isn't going on with your shoulder and how to treat it.
It may be that you have more damage than just a torn trapezius muscle, could be tendons and ligaments involved and possibly something with the rotator cuff.
Fibro will make the pain worse, and muscle pain can have a burning component to it, but so can compressed nerves.
it sounds like a ortho doc that I suggested will want new x-rays done and probably and MRI as well.
Get to the type of ortho I suggested ASAP and let us know what the results are.
Fran