Dont worry, I did. I actually passed out twice, both times in a hot shower in the morning. It started with feeling light-headed, then I felt hot, then sick, then I got the tunnel vision/lights starting to cover my eyes!
The first time it was such a horrible experience, I went straight to the doctor, who said I probaly had a virus - I was only 6 weeks gone. Then it happened again about 2 weeks later. My midwife said it is fairly common, and another delightful symptom!
I havent had it since, but if I dont eat regulary, especially by lunchtime, my blood sugar crashes, and I go shakey and light-headed. I think im going to check with my midwife about diabetes.
But try not to worry - as long as you can feel it coming on, and can get yourself safe, you should be fine. Maybe try having a sugary juice drink with you, or piece of fruit, and see if that helps you feel better xxx