If, indeed, it is stress related, I can empathize. I too experience this malady every now and then. I find that a good, hard, sweaty workout help relive the stress and the tension. Often this requires a bit of working through the pain, and I usually start the workout slowly. Just two days ago I awoke to that knot and pain between the shoulder blades and running up through the neck. I was pretty sure it was related to stress at work. Got on the bike, and it hurt like the dickens for about 20 - 25 minutes, but I kept pushing through. By the end of a brisk 20 mile ride and a hot shower, the pain and knot were gone.
Good luck with your attempts at relief.