It’s natural to move when you sleep but there may be medical conditions that support sleeping on your back. The following methods can help you to avoid shifting while you sleep: Placing a pillow underneath your knees Placing a pillow under your lower back Creating a fortress of pillows around yourself. Of note, some people find that back sleeping increases discomfort in their lower back, but prefer to sleep on their back anyway. In this case, placing a pillow under your lower back while you sleep might help.