Sharp burning pain under right armpit only when i move my arm a certain way and nit all the time. just once in awhile. very painful.

Shoulder pain: To help more would need to know the "certain way" you move it Armpit pain is usually from the joint. Intermittent pain would indicate a capsular tear. If it gets bothersome enough to consider surgery (arthroscopic, outpatient)then get an MRI and see a surgeon. Otherwise avoid using it the "Certain way" for a few weeks to let it heal. You may need a follow up. Let us know.