Thanks ladies! I don't know if this is sciatica or not. It does not shoot down my leg, which I thought was quite common with that. It is more like being stabbed right at the base of my spine, towards my left hip. It hurts when I put weight on that leg, and it can make me catch my breath involuntarily. However, I have tried sleeping with a pillow between my knees, and so for, so good! It hasn't happened again. Hurray! Let's hope it stays that way.