I am having an acute lower back pain and particularly while sleeping. It makes hard for me to even bend in bed. And its happening for last 3 years. I go for running and exercise in the morning. And after doing a much research on what would have caused this pain, I have realized I used to do sit ups and could listen to a popping sound that my back used to make. As if now I have stopped doing sit ups, but the lower back pain is not going.