After a few hours of sleep, whatever side I lay on is hurting. I change sides (and have even tried sleeping on my back and stomach, but I again wake up after a couple hours or so and I am hurting on the side I am on at that time. I have been up for several hours now, and the side that I slept on last is still hurting. This has been going on for over a week now. Please advise about some possible causes for that. Thank you for your time.