I can't sleep with my arms down at my side.I have recently had success dealing with the same problem and here is what I did. I read another thread here that mentioned the hackers diet. I looked it up and reviewed the exercise plan. I thought that I would try the exercise routine every day at a minimum.
I have been using the exercise plan since March 10th and it has helped a lot. I'm at level 12 starting today. My shoulders feel much better and i can sleep normally without pain or discomfort.
I will admit that I have adjusted the program to fit my circumstances. In the first 2 weeks I progressed many levels because it was too easy. I do regular push-ups now and use crunches instead of sit-ups. I hope this helps with your problem.