Well, except for that time in Paris. When I was in the sixth grade, living in West Germany, my parents sent my two older brothers and I on one day trip to Paris. The bus tour dropped us off at the Eiffel Tower for a couple of hours. On the second deck of the structure my brothers and I were playing around, looking down over the railings, and then whipping our heads around to stare at the top of the Tower our backs leaning against the railing, and then rolling back around towards the ground. For some reason this stupid maneuver began to make my stomach flip. That eventually led to my brief experience of being an eleven year old lost in Paris.
Outside of that incident I have never had a problem with heights. I've never been a fan of falling, but heights were not the issue.
Lately, however, that's not been the case. I've been getting really queasy with certain things; the top of a ladder, hanging Christmas lights on the roof, tightrope walking between the Twin Towers, or just watching YouTube clips. It's getting bad.