Has your doctor checked your blood pressure? I'm sure he has....but it was the first thing I thought of when you said you collapsed.

You might need to go to the ER if it happens again. I'm going to suggest that you start a journal and keep detailed notes of all your symptoms and when these episodes occur (date and time). These will be invaluable to you when you see your doctor. I have the same problem with remembering when things happened. If I didn't write it down it may as well have never happened.

I really hope you get some answers soon.