What would cause pain and tightness from right deltoid thru trapezius, up neck and down right shoulder blade? Mri shows no nerve impingement in neck. Problem has lasted nearly 3 years. I am 28 and male

Cervical strain. Cervical muscle strain is more common at your age than nerve impingement. It may come from just straining the neck or compensating from a shoulder injury. Because it has lasted 3 years, you should be evaluated by a specialist. Heat and cold may help - especially heat at this stage from topical creams or hot packs. Formal physical therapy may be necessary.
Sick scapula. There is a syndrome called sick scapula when your shoulder works improperly either due to injury or imbalance . This is usually corrected with very specific therapy. I would see a shoulder specialist who can direct the appropriate therapy.