I tried chiropractors, after my Doc friends told me I deserved it for never warming up. At least 10 messages did nothing, except to create a dull feeling.
Now I contantly stretch to keep the back muscles loose. Figure a knot is tight. I surfed for 25 years, 5 days a week, so have calcium buildup on my shoulders and back of the neck.
I"d sweat thru some pain, try swimming freestyle and breast, to hopefully loosen that knot. It will be fragile for the first month or so, almost twinching, but keep up the loosening motion work.
Hope it helps. You had your's for 2 years, so it might be structural.