I have pain in m lower back and front on my left side and pain at the back is worse when i walk what can it be?

Doctor can examine: The more common causes of lower back pain include: back muscle strain, back ligament sprain, fractured vertebra (spondylolysis), slipped vertebra (spondylolisthesis), herniated disc, spinal stenosis, spinal arthritis, urine infection, kidney infection or stone; tumor in the spine, kidney, or elsewhere; fibromyalgia, etc... With such a long list of possibilities, one's doctor can examine.