For The Past Week, I Have Upper Back And Left

For the past week, I Have upper back and left shoulder pain causing radiating pain into my neck. (I can feel knots in my muscles). I have used a heating pad and my Shiatsu and massaging chair, but it has not helped. The pain is spreading around my arm and into my chest. It hurts when I stretch and/or lean over. Is it possible it is more than simple muscle pain? I have not performed any exercise and work at a desk.