Thanks for query,
It seems that you might have some problem in your spines giving rise to this problem.
You have not mentioned your age,if you are elderly then you might have some osteo artheritis,osteoporosis
Go for X ray
lumbar region to find out the cause.
After report go for the treatment accordingly.
Meanwhile you use hard bed for sleeping,
Go for Back extension exercise.
If require take some pain relieving and muscle relaxant
Ok and bye.