It is most likely due to your posture and long hours of working on computer. I am having same problem since 2 years. Keeps changing in severity but some pain and stiffness is always there. One year back i met a doctor for this problem. He gave lots of medicine and asked to go for physiontherapy. I took medicines for 2 weeks but never took physio as it was very time taking affair. Pain reduced at that time but did not go away completely. Calcium n all is not going to help. Rub some gel like relaxyl at night. That helps me and see if u can follow all the good posture advice. I try to follow as far as posible.
It can be due to your computer work, or may be poor posture while sleeping or might be due to a more serious reson like spondylosis. Get yourself and appintment with orthopedician, i guess it will help you better to solve the problem.