I get really bad Sinus headaches that make me feel the way you described. Just something else to look into.

I used to get what the Doc called Optical Migraines, I would loose half of my vision (literally one side or the other) but never had the pain. When my vision would start coming back after about 30 minutes, I'd get extremely sick for about an hour.....It was weird b/c I only experienced that about twice a week for about 3 months. That was around 10-11 years ago. The Doc said at the time they were from stress. Makes sense since that was the time I first went off to college.