What Could Cause Physical Exertion Mediated Back Pain?

Hello doctor. Im 37yrs and 181cm tall. my weight is 110kg. i started experiencing back pain on my left back about a year ago. The pain usually decreases when i take anti inflammatory medication but resurfaces after about 3-4 days. It gets worse when i do exercises like table tennis which i love to play. I work 12-hour shifts a day and most of the time im sitting. Any clue whats going on? i ve had an x-ray of my lumbosacral region and it came out good. Sometimes the pain radiates to my left groin. I would appreciate any explanation or solution.