I have pain at the top of my right arm -- not in the rotator, and not in the shoulder, but in the muscle at the top of my right arm, right below the shoulder. It hurts when I put my arm straight up to take off, or put on, an undershirt. It also hurts when I lay on my right side while sleeping. I have had the pain for about 2 months. I am 54, non-smoker, exercise every day (stretching, push ups, and 1 mile run on a treadmill. Thoughts?