I'm glad you're enjoying it.
You can come out to Adam whenever; it doesn't matter. But you need to come out to someone else early, also, and get that person to go to Q&A with you instead.
Also note that Adam is less a full route than a secret ending, so once you think you've satisfied his requirements, you have to play through the rest of the game. If you succeeded (and got sufficiently close to him throughout the game), he'll ask you out when you return from winter break (after the usual "end" of the game).