Hi!
I too suffer with shoulder pain along with neck and under my shoulder blades. Two weeks ago I was in so much pain with my right shoulder/neck that I could barely dress myself. In the past my doctor has given me injections of Marcaine. It's a long acting, time release numbing agent. He injects it into the are that's causing the pain and it normally helps considerably. He first injects a local numbing agent so the Marcaine injection is more comfortable. By numbing the area is gives the muscles or swollen area a chance to relax and heal. It's worked for me several times.
Like mentioned above, there could be so many things causing your pain that you should have a doc look at it to see if they can get down to the cause and maybe address that issue. If it's fibromyalgia pain then the injections might be the way to go.
For those who want to make their own heat pack..... here's a link that might help. These are the kind you fill with rice/corn/or other items and then heat in the microwave and use. Ahhh, they are so soothing and stay warm for a long time.
tipnut.com/make-your-own-microwave-heating-pad/ Chutz