Im a 49 yo male who is experiencing dull pain intermittantly to left shoulder region. It seams skeletomuscular in nature as I can cause it to worsen with certain movements though it is at its worst while trying to sleep. I would normally not be concerned but for the unusual muscle spasms in my left pectorals, triceps and lats. I have a physical job but remember no insult. Thinking it may be an impinged nerve... any ideas?