I mean, "no" was an honest answer but "not yet" would have been the more accurate answer lol. You're right that she probably didn't think about gay sex much but for sure she knows that it's possible. It might be hard to imagine but your mom was young once too and did all the things young people do so you have to give her some credit. Her baffled look was probably more of her processing that you might be/are gay, plus truly wondering/concerned if you've been doing the deed with other dudes. Anyway, I can't begin to imagine the awkwardness you must be going though but hopefully it gets better from here. Good luck my man...