Nancy
My daughter went through what sounds like the same thing. She would be fine sitting in a chair and all the sudden she would slope over, as if she fell asleep. She was back and forth to doctors for several months, but they had no clue as to what was wrong. Finally a doctor at NIH sent her to a migraine specialist. When we went I took all the records that I had taken during this time from monitoring her blood pressure, paulse, heart rate, which was racing during these attacks, her bllood pressure also was going through the floor. To make a long story short, this specialist put her on Inderal, for vascular migraines; and once they got her on the right strenght she has been fine now for about 15 years, as long as she doesn't get over tired. I hope this helps. Maybe you can get your doctor to refer you to a migraine doctor and have them check it out. Good luck to you.