As per your case history ,Back pain is very common in IT professionals ..it can be related with knee pain also.on your case back pain may be due to poor posture,lack of exercise resulting in stiffening of the spine and weak muscles. Sitting for long time leads to muscle strain..
Next Steps
1:keep set your alarm for 30 min.after that take a exercise break ..do some warm up exercises ..for that consult me via practo .I would suggest you the best over there..
2:make some ergonomic changes in your areas.like how far your desktop screen is from you.. how your using your key board ,mouse ..how much effort did you apply for doing. your all work.
3: you should maintain correct posture .
Health Tips
you should consult a physitherepist if your pain is really bad ,lasts for a long time.