What Causes Severe Pain In Shoulder And Bicep?

I have had shoulder as well as Bicep pain for working on 6 months it seems concentrated on my bicep but it seemed to have occurred after a series of immunizations to start employment at a local hospital ,, maybe coincident not sure ,, anyway not sure if its a muscle to immobilize it or exercise it slowly seems to be gravitating all the way from shoulder to even forearm, any advise Please