I used to get headaches / motion sickness playing fps games, then I learned to sit farther back from my monitor. It helped quite a lot. Also, take breaks. I spend lots of time in front of my computer, doing school, browsing internet, watching netflix, and gaming.
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Do I have HFA? Nope, I've never seen a psychiatrist in my life. I'm just here to talk to you crazies. ; - )