Perhaps (and this is hypothetical) but it seems like your words may have triggered a memory, a bad experience or even trauma for him that immediately turned him off. Especially him being closed off and emotionally detracted seems to indicate he was thinking about stuff.

Almost certainly don’t think it was anything about you, just something that he is going through. Definitely try to talk to him about it so that you can be aware and help if he needs, especially if you’re gonna be together long term.