It sounds like you had a good result by a good surgeon. You may have two issues as residuals. By waiting so long, you may have some chronic radiculopathy (see website). The compressed nerve will heal somewhat but may always be sensitive to too much stretch.
The lower back pain results from the disc itself (or possibly from the facets but facet pain is less common in the lower back). Core strengthening is one of the keys to stabilizing the back and should be part of your routine exercise.
If your symptoms continue to irritate you, you could consider a highly selective nerve root block at L4-5 right (see website for explanation) to see if the lateral recess stenosis at L4-L5 is contributing to your current discomfort.
Good luck.
Dr. Corenman
PLEASE REMEMBER, THIS FORUM IS MEANT TO PROVIDE GENERAL INFORMATION ON SPINE ANATOMY, CONDITIONS AND TREATMENTS. TO GET AN ACCURATE DIAGNOSIS, YOU MUST VISIT A QUALIFIED PROFESSIONAL IN PERSON.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.