What would cause pain, tingling and numbness behind left shoulder area?

Pain numbness tingli. Could be musculoskeletal from strain-more pain w/ ar mmovement?- or I have seen left shoulder pain ( by scapula) from gastritis, H pylori . Could try ranitidine for gastritis, tylenol/ motrin ( if not allergic) for musculoskeletal pain . rarely could be neurologic like MS( all else negative- this position is no usual) or vascular. f/u/w/ doc.