amonkie, good point on the spelling, I guess I should read things more closely..
Your experiences sound the same as mine. Bathtubs, getting up quick, etc. I've always been under the impression that they are completely normal and everybody gets them. In fact, when I get one I tend to shout "head rush!!" so people know what's going on. My family does this too.. So I know they get it often. I don't think anybody that gets these has a health problem, but I'm really curious now to know what causes them.. hmm..