Not telling coworkers we're TTC

So my boss flat out asked me today if we were trying to get pregnant. Isn't that against some law or something?  I think I probably looked like a deer in headlights and stammered something to the effect of "yes, we'd like to get pregnant at some point..."  or something equally stupid.  It totally threw me off guard!  No one at work knows that I'm TTC.  Part of the reason for that is because I don't want to have to deal with questions about how it's going or why I'm not KU yet, and don't want to hear "just relax and it will happen!" or other assorted "helpful advice". The other part is because I think I will likely become a SAHM once we have a baby but am not going to advertise that fact at work until I have to.  
I feel...exposed now or something.