What Do Neck Pain With Shoulder And Arm Pain Indicate?

Question : I woke up two weeks ago and thought I just slept wrong and ended up with a sore neck. My neck hurts on the lower left side only a little now especially if I lay my head back but I am having severe pain over my left shoulder and upper left shoulder. The pain goes down my left arm to my hand when I bend over or hand my left arm down. The pain lessens if I raise my left arm up like I did when I was in school. I have RSD and it usually only affects my right arm but my left arm feels like it is on fire from the top of my shoulder to where a short sleeved shirt would end. I have been alternating ice and heat and I have also been doing light stretching, massage and pulley exercises along with a tens unit but is not helping, just makes new hurt even more. The last two days it has been pretty severe and I cannot do anything but stay close to the heating pad. Thank you.