I too have a history of passing out. It actually all started in 2nd grade, I am now 25. Starting when I was in 2nd grade, I had 2 or 3 fainting spells a year and my doctors never could find out why. When I started menstruating the spells would happen 2 or 3 times right after another 2 or 3 times a year. My gyno had told me that I was having all these symptoms (excrutiating pain, nausea, diarrhea, fainting) because of an irregularity with my menstrual cycle. That was when I was 18. Since then I have fainted a couple times from IBS, and a couple of times from being nervous when getting tattoos worked on. My present GP told me that he thinks my personal fainting episodes are from a vaso-vagal response. If I am in pain, get up to fast, get myself too worked up when nervous or anxious, or when I am sick. He told me not to worry about it that some people are just that way and to take certain precautions; take my time rising from a laying position and in other situations that if I feel it comming to act as soon as I can, if I can, so that I don't hit my head or injure myself in anyway. The first time I passed out I was getting ready for school, brushing my teeth and my mom just so happened to be walking by the bathroom door with a basket of laundry in her arms and caught me RIGHT before I would have practically knocked my head off on the sink! Unfortunately about 3 months ago I awoke in the middle of the night with MAJOR pain from a IBS attack and ran to the bathroom. The next thing I know I woke up all cold and sweaty with a HUGE bump on my head, the bottom half of the bathroom wall is covered with tile! That hurt for a few days! But I have to say that waking up from a fainting spell feels really good! Sorry to have go on for so long, but once I start I can't stop!