What Are Some Causes For Lower Back Pain On The

What are some causes for lower back pain on the left side that has lingered for 4 weeks. Also a few days ago I had a cramp on the right side of my back. Went to doctor 4 weeks ago and he said that it was a pulled muscle from x-ray and gave me a shot and a prescription. I have gone to the chiropractor several times since then but still no relief.