What is causing Horrible back pain every morning?

Every morning my husband wakes up in terrible back pain, I mean it is just Horrible! By the afternoon his back is much better, when he goes to bed he wakes up in terrible pain again. We have tried 3 different beds, different types of blankets, quilts, bed cushions, etc... Even tried sleeping on the floor, and the couch but still the pain is there 98% of every morning. I began to feel it was the way he sleeps, like laying on his side, or maybe there was a certain position that is hurting his back. I have watched him sleep to see if I can find a pattern but there's nothing. DOES ANYONE HAVE AN IDEA HOW TO STOP THIS? HAS THIS HAPPENED TO ANYONE ELSE BEFORE?