Your symptoms are classic motion sickness. This is what is happening; your eyes see what is happening on the screen and transmits that to your brain. Your body also transmits what it is feeling (e.g. your'e not moving) to your brain. Your brain looks at these signals and thinks, "that isn't what happening - I'm not running and jumping and turning etc." My eyes are telling me this, but my body is telling me nope I'm not moving, I'm just sitting here. So there is a confusion of signals between what your brain thinks you are doing and what your eyes and body are telling it. The result is generally nausea, sweatiness, and dizziness. This can last for hours. That is why at the initial onset of these symptoms you should stop what you are doing and look at something real. Not your computer screen. If it is day light out, then look outside. If nighttime look into the far end of a large room. Make sure to breath and don't look at the TV or anything moving. Get some cool air if possible. The key is to look at something stationary and try not to move too much. Let the signals between your brain and body become de-conflicted.