There are many reasons for having lower back pain left side. One may be the same as mine and it is due to my sleeping habit and moving in my sleep. Since I have started sleeping with a pillow between my legs I am able to stop turning in bed and able to sleep better since my back is now in better alignment. I did not go out and spend a lot of money on one of those expensive pillows I simply went to my local store and bought one for about $8 and it seems to work just fine for me.