what is the reason behind reoccurring of my side back pain?

I don’t know the specific reason behind this but whenever I think that I have recovered from my side back pain it just reoccurs again. When I continue taking the medicines like pain killers and therapies that doctor had prescribed to me it seems like I have totally recovered from this pain but when I leave these medicines and therapies my side back pain reoccurs in not more than two weeks. So I want to ask this from you guys, what may be the reason behind reoccurring of my side back pain?