Most of your pain is in the lower back. Most likely, the pain is degenerative disc disease (see website). You do have some left leg pain and numbness which is likely from a herniated disc compressing the root. Since however most of your pain is lower back, the disc herniation might only be a small part of your global problem.
I do believe that an MRI and then an epidural injection would be helpful if indeed you have a herniation associated with degenerative disc disease.