Have you experienced this? What's it mean? I was riding the bus reading a book when a sudden wave hit me - I felt nauseous, shaky, my head was full of pressure, I had to breathe faster, when I stood I was afraid I'd fall over, I was really dizzy. I know I wasn't dehydrated, and I'd eaten today - not a whole lot, but some. Any idea? I ate when I got inside and sat down... but I'm not sure I'm better.