Hello there. You seem to have developed cervical spondylosis. Stiffness in neck, difficulty in neck movements and pain radiating towards back of head all point towards it. It can be confirmed on a cervical spine X Ray. If it is confirmed you will have to attend physiotherapy for neck exercises and application of short wave diathermy. Taking muscle relaxant s will also help to relieve the stiffness. Tab Myospas is a good option. You should also take care to maintain a good posture and not hunch while sitting or standing. Take break every one hour if you work for long hours. Try to sleep with cervical pillow. I hope that answers your question. If you have any further questions please feel free to write.