Debbie:
I sympathize completely! I have missed work all week for the exact same thing. I'll be seeing the chiropractor for the third time in three days today, and I had a massage last night (good health plan). The chiro was able to determine that there is "nerve interference" going on with me, and with the symptoms in your shoulder that may be happening in your case as well. If so, do not hesitate to get some professional attention, because a slightly bulging disk could be the cause and they are nothing to play around with. I am not sleeping because if I roll over when alseep I seem to aggravate the situation and wake up worse and in total spasm from the ribs up on both sides.
The chiro said sleeping on the back with a little neck support and the head on the level of the mattress more or less is the best way to maintain neutral alignment. Then the muscles will back out of spasm and the vertebrae can try to realign. Unfortunately, I roll over unconsciously and zap myself. Last night I tried sleeping in an arm chair, and managed to doze a bit, but at least I didn't get worse. I'm hoping the spasms are down enough today that the adjustments will hold and the arm symptoms will subside.
A good body worker should be able to get that knot down for you, but you may have to see a physical therapist for instructions on how to reintroduce upper body exercise once you get the cause resolved. Keep experimenting with your pillow(s), and remember the goal is for your spine to be in neutral alignment (as if you are standing up straight with perfect posture) while you sleep. If you are in spasm it's almost impossible to tell what alignment you're in, so ask for help from someone you live with.
On the other hand, if there is no spinal involvement, I would just try to get the knot worked on, stretch the traps aggressively, and work the shoulders very conservatively, paying close attention to what moves aggravate your injury. If you like yoga there are lots of good neck exercises and stretches.
Sorry so long-winded. Good luck!
--Ann