What Causes Pain In Shoulder Radiating Down The Arm?

I have been having daily shoulder pain that seems to radiate to the front of my arm and to my wrist on my left side. I have had problems with my wrist and elbow before, the shoulder started when I started going to physical therapy for my neck. It started popping and hurting then. It stopped for a while when I stopped doing the exercises. The pain is now all the time, and it radiates to my neck Happening right now . This all started up after I had a colonoscopy two weeks ago. I am taking vicdin I have from a previous surgery. I have been woken up by extreme pain in my shoulder and heaviness in my chest. I just cant seem to shake this pain it just doesn t go away and even with the pain meds its still at a dull ache. Not very happy - I have a ton of doctor bills and don t want more if not nesicary. How likely is it to be more that a muscle thing? its not my left side, my life is doable - just not productive, Dawn