ahh ive fainted and nearly fainted a couple times, yesterday was one actually.
it mostly happens to me when i get out the bath lol. to help make sure you always have water and a snack as said above as it could be because your sugar or water levels are too low. Don't have a bath thats too hot (thats my problem) and when that feeling comes over you, try and find somewhere to sit, put your head on your lap and breath in and out until the feeling passes. xx