What Causes Severe Pain Under The Shoulder Blade On The Back?

I have severe pain in my back, right side just under the shoulder blade area and up to the right side of my neck. I also have pain in my right arm and numbness when I reach forward,upward,or use it for anything with excessive strength. I think my ulna nerve is pinched but worry that my neck vertebrae might be compressed,inflamed,or a disc ruptured. What do you suggest I try to relieve the pain. I m disabled with Primary Lateral Sclerosis and have to make advanced plans to go to a doctor s office