Upper back pain in the same spot present for one year. on right under shoulder blade. not present at rest only with activity. ct six months ago clear.

Seems like bursitis: There is a rare cause of pain, due to the prescapular bursitis, in which most tests come back as normal. You have had the MRI & chest xrays, probably were negative. Hopefully the same MRI was of the rt scapular area. I would suggest getting reevaluated & probably get retested again, if pain continues after 3-6 months. With the normal tests, rest assured that nothing serious is going on.

This could be the : Result of a chronic muscle injury or referred pain from neck. It is something structural meaning muscle or skeletal as it occurs with activity & better with rest. It may be a local muscle that was injured & is now shortened due to prior injury or a cervical (neck) spine structure referring pain to this region or even a shoulder issue including a nerve entrapment in the shoulder. See orthopedist.