This is due to your long sitting posture at work. This is called as ergonomic hazard. Back becomes painful due to long time work in same position /lack of exercise and strength/muscular weakness. Consult a physiotherapist.
Next Steps
Go to a physiotherapist.. Ultrasonic therapy +IFT +Heating therapy +some strengthening as well as stretching exercises will be helpful for sure.
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no long sitting /standing /walking/travelling /driving +no cold exposure +no weight lifting /forward +correct posture (sit tall) with foot rest.