Amy Rose, does this happen at any other time? You could have any one of a number of problems including low blood sugar, low blood pressure, anemia, etc. I would see my primary care provider and get checked out. The symptoms you describe sound very similar to the symptoms I get if I'm inactive for too long. I have a blood disorder that can look like anemia in blood tests, and the symptoms are similar. What works for me is proper nutrition and regular exercise. I always know if I'm not getting enough of either, I have "grey outs" after standing up from sitting for a while. Vision goes to grey or even black, buzzing in the ears, loss of equilibrium, and on rare occasions legs buckling - "Face? Meet coffee table!"