What Causes Severe Lower Back Pain?

I am a 52 year old man who’s been suffering from severe lower back pain for about 10 years now. Initially, 5 years ago, it was diagnosed form an MRI to be a disc prolapse around my L2, L3 area. Three years later after conservative treatment, the MRIs showed there was no more prolapse as the pain abated. However, it later took a new dimension as I now developed heat in my left leg and inability to stand in one position for more than 15 minutes as a result of pain around the lower back area extending to the left legs. The last two MRIs done two years and six months ago respectively were considered clean by the neurosurgeons. They however recommended diclofenac either of Pfizer Arthrotec 75 mg or Novartis Voltfast 50mg once or twice a day throughout my life. This does the magic and manages to keep the pain away. However my fears are, will this dosage not likely affect my essential organs in the long run? Is there something else I can consider as this pain has reduced the quality of my life.