What Causes Pain In The Shoulders And Neck?

I'm being treated for a 7 yr. history of back/nerve pain and muscle spasms. Have bad arthritis in neck, 2 herniated discs in lower back. Was having muscle spasms and stinging in my left shoulder blade that traveled under my arm pit and into my left breast about 8 months ago. Had heart tests done and they said I was fine. Have had two steroid or cortizone shots in my left shoulder blade in the last 6 months which took away the pain but yesterday my left side started feeling like my shoulder was tight and knotted, my neck kind of hurts and my left breast had a sharp, stinging in it off and on (kind of like an electrical shock feeling). Do you think it might be muscle spasms in my chest again or should I go get it checked out.