In addition to Oak's suggestion, I think you need to be mindful of your neck posture when you are seated. The tendency is to hold you head too far forward. Ideally, your ears should be balanced directly above your shoulders. Of course there are other aspects of seated posture and alignment that you should be mindful of, too. I would encourage you to start there before trying a stability ball. Some of what I have read about that suggests that people with existing injuries should not use a stability bar.