Just leaving this here in case it saves someone else a little suffering: it was life changing to start sleeping with a pillow between my knees. I used to wake up with debilitating lower back pain every morning, which I worked through with stretching and yoga and such but then I saw a commercial for one of those bowtie shaped foam pillows that go between your knees and figured "what the heck" and ordered one. It was weird at first but seemed to help a bit, then one night I came home late, tired, and couldn't find the thing so just jammed a regular pillow between my knees--the following morning was the first time I woke up without back pain in years. It's definitely hard on the pillows so now when I buy a new pillow for my head I demote the old one to knee service.