On doing ergonomic assessments, a very common flaw I've seen is to have the screen too high. The center of your screen should be about 15°-50° below eye level. There is an old-school mentality that your posture should be pure right angles, and the center of the screen should be at eye level. For most people, this is a continual strain on the muscles of the head, neck and upper back, and can lead to headache, neck, or back or shoulder pain or problems. We are not built at right angles, so you don't have to set up your computer at right angles. Take out your phone and look at it, the natural tendency is not to hold it straight up at eye level.. Previous versions of this advice were, "where would you hold a newspaper?". Ask your parents or grandparents if that's not a familiar words or concept, but as you can see in the stock images below, this is how we used to access news sites:
If changing your monitor makes it worse, or if you still have pain, ask me about it, I answer emails and calls.
Yours in health,
Dr. Charlie Ginsburg, DC with Physical Therapy privileges.