Many of us suffer from tight traps because we are always bunched up over the computer, Iphone etc. I have found for myself learning stretches for upper traps and strengthening exercises for the lower traps will help illiminate the pain. Relief does not happen over night but I manage the acute episodes and prevent escalation. I also use a tennis ball within a sock up against the wall to relieve pressure points or knots. I put my back on the ball and roll and massage the painful tissue.
As a student and a surfer I experience a lot of trap tightness and at night I apply Tiger Balm. It gives me immediate relief and loosens the muscles. You may want to check the ingredient label before applying. What works for me may not work for you.
Fibromylagia and arthritis are other stories, one I am sure you have discussed with your physician. Self care is about adequate rest, regular exercise, stress reduction, eating healthy, support, and doctor consult.