I have back pain for many years from now. I don't know exactly when it started and what causes it to pain. I remember slipping in a toilet and my back hit the edge of the bath tub. I didn't feel much pain at that time so I didn't consult the doctor to have a check on my back to see if there were any injuries on my back. But i started to feel pain on my lower back a few years back. This pain would surface when I walk or sit for a long time. And early this year my lower back does not hurt as much as it used to hurt last time. But this time round, the pain is on my left side of my back. The pain is located near my spine. On the left side only. Does anyone know if this normal? Or is it something that I should refer to the doctor immediately?

Thanks.