My upper right shoulder area has been hurting for a few months now, it feels like a knot or something, what can it possibly be?
Trigger point. From your description this sounds like a "trigger point" in your trapezius muscle. This is a painful spasm of a small area of muscle which causes the "knot". The knot is usually tender and pressing on the area can cause the pain to radiate. Treat it with direct pressure, heat, massage and if no relief, injection of the trigger point can be done. Get it examined to make sure that is what it is.