You might wanna see a doctor.
A buddy of mine had problems w/ a shoulder (not necessarily your problem) and he had severe pain. Then, things progressively got worse & it would become dislocated in the middle of the night while he slept. (He couldn't side-sleep at all)
Finally, he gave in & let the doctor have at it. They re-strung up his ligaments so that his shoulder came back up, he could sleep again and is now pain free.
Doctor could do a scan to see if there's anything he can do.