If your job requires that you work at a computer or if you spend a lot of time on the computer as a hobby you stand a good chance of experiencing fatigue, neck pain, pain between the shoulders, carpal tunnel syndrome, and many other syndromes.
To avoid fatigue, stand up and stretch, at least every two hours. Place the monitor at eye level and directly in front of you so that you are not twisting your neck all day (a common problem with bank tellers, librarians, etc.). Keep your keyboard at a height so the forearms are parallel with the floor and the wrists are kept straight. It is a good idea to stretch the shoulders, arms and wrists along with the neck and back periodically during prolonged computer use.
If this does not help have your workstation ergonomically checked.