For People with Back Problems here is A Sleeping Position that Works

This is a very simple comfortable way to sleep if you experience low back pain. It works if you are experiencing back pain. Simple place a flat pillow under your knees when you are sleeping on your back. If you are side sleeping, sleep with the pillow in between your knees.

You can get more fancy and use a wedge made our of memory foam. For me personally, I sleep on a very soft flat pillow. This makes a big difference in how well I sleep. This position literally takes the pressure off of your lower back.