Hi, Shirley. I can't sleep on my back at all. Wish I could. I had back surgery that went bad and sometimes it feels better, but I'm a side sleeper. Try putting a couple of pillows under your knees where they're kind of at a 45-degree angle. It takes the pressure off the bottom part of your back and makes you much more comfortable.
You can try to sleep on your side and then put a pillow in between your knees and thighs in order to reduce back pain. You can also sleep on your back and place a pillow below your knees, which help to sustain a normal curve on your back. For reference, go to http://www.mayoclinic.com/health/sleeping-positions/LB00003_D.