Hi eektvas,
Given the few details that you've provided, I can suggest a couple of potential 'broad' solutions based to the physical issues that you're experiencing:
1) Be mindful of how close you're sitting to the computer screen. Over the course of the Exam, you'll be staring at that screen for the better part of 4 hours (and the final 75 minutes will be during the Verbal section when you'll be the most fatigued). Leaning back from the screen and making sure to take plenty of notes on your pad (so that you're not constantly staring at the screen) will probably help.
2) You might be getting dehydrated during the Exam. Make sure to drink plenty of fluids/water before the Exam and during each of your two 8-minute breaks. This will likely also require that you use the restroom a couple of times on Test Day, but that is a fair trade-off to avoid these symptoms.
GMAT assassins aren't born, they're made,
Rich