Correcting Chronic Pain

My husband has been suffering from a chronic pain in his shoulder for months now. Since he does so much heavy lifting at work he thought that was a major reason for the pain, but it turns out a lot of the problem was from pressure when he slept. He always sleeps on his side. He hates sleeping on his stomach, and can't seem to stay on his back so he ends up on his side and that puts a lot of pressure on his shoulder joints. One recommendation was to get a foam mattress that would be more apt to mold to his body rather than increase the pressure by resistance like a spring mattress would. We are checking into that option as well as a few others. He was relieved to learn that it was something like that rather than the strain of lifting and pulling that he does daily in his job as a paramedic, but it's really important to correct the reason no matter what because it definately effects the way he is able to do his job.