Happened to me today, and it made me feel soooo affirmed

I went to Planned Parenthood for an STI check, and I, a trans woman, was asked when I last menstruated. I had a light chuckle before clarifying I was a trans woman, and she said "Oh, guess we don't have to worry about that then!" Felt incredibly affirming, because I passed well enough even after 15 minutes of conversation that she didn't realize I was trans! Especially funny because it was at Planned Parenthood of all places, so she's obviously dealt with a lot of trans women.

I struggle to think I "pass" to other people, but I've had these kinds of things happen enough that I'm maybe starting to believe that cis people really can't tell lol.