I paused a moment because part of me was not totally sure what she was asking.  I was fairly sure I knew, but also knew I would sound stupid if I guessed wrong. But when she said the “inches or centimeters thing,” it could not have been more clear. I was just surprised that a “proper girl” like her thought this way and about these things. I thought if SHE thought this way, then all girls must! 
For a long time, a really long time, I had the suspicion I might be a bit smaller than most. Hard to say where one gets an idea like that initially, but I did. Later it was confirmed in the locker room where there were some impressive guys. Most seemed at least average, but some were, well, quite big. I learned to reach for the towel quickly to cover up.  So I already had a bit of a disposition of “concern” before Michelle happened along, in all her beauty.
For a moment, I literally did not know what to do or say.  It felt a bit like when you are at the beach and get knocked over by a wave. Until you get your feet solid, you feel lost and like you don’t know if you will survive. The silence was getting awkward and the longer I did not speak the more awkward I felt. She on the other hand seemed fine. Calm. Confident. Just fine. I had to saysomething!  I was starting to seem stupid. I did not know whether to say the truth or, rather I did know not to say the truth but how much to lie was not clear. I figured if I lied a lot and then some day she discovered the truth that would be awful.  On the other hand I figured if I told her the truth I would be a minion. A joke to her.  Not “boyfriend material” or even “friend material”.  I knew I was on shaky ground with this gorgeous girl as it was.  I did not want to make it worse. How did she ever get this much control. I tried to sound casual but failed miserably.  My goal was to give the impression I hardly ever thought about “size”.