Sleeping on your back isn't necessarily harmful, but it leads to back pain in some people. You're also more likely to snore because the relaxed tissue in your throat blocks your windpipe. Sleeping positions can be a matter of habit and tricky to break. When you're in deep sleep, your body could move to its usual, comfortable position without a little intervention.
Stuff a tennis ball into an old sock.
Attach the sock to the back of your pajamas or sleep shirt using a safety pin. Wear the pajamas to bed, so that when you attempt to roll over on your back, you'll feel the uncomfortable tennis ball and correct your position.
Lie on your side in bed. Place a pillow behind your back to help prevent you from rolling over onto the tennis ball. If the pillow stops you from moving, you can avoid the uncomfortable feeling that occurs when you roll over onto the tennis ball.
Place a pillow between your knees while lying on your side if you suffer from back pain.
Ask your partner to wake you or encourage you to roll over if he notices you're sleeping on your back.