I'm a gemini ascendant with a scorpio sun so I get both energies. My gemini self can be very flaky and erratic when communicating with other people, even though the scorpio in me hates it when others do that to me.

But nobody here is going to be able to tell you for sure what's going on with him. This might be absolutely nothing and things will be back to normal soon, or he might be getting bored in this relationship which is a very gemini thing to do and I wouldn't take it personally at all. Especially from the story you told about why he stopped talking to you, it almost definitely has nothing to do with anything you did wrong.

Also, I don't know if you know this but there's very little you can tell about how two people will do in a relationship by learning just their sun signs. Astrology is much more complex than that. It'd be better to do a synastry (just search astrology synastry calculator) and look especially at relationship-related signs like mars and venus

All that being said, the advice I want to give you isn't astrological. You need to communicate with this guy and tell him what you're thinking instead of trying to guess. Something like "You've seemed more distant since we had that conversation, is anything up?" and letting him know you're concerned is a perfectly reasonable thing to do and will probably be the only thing that gets you answers. Being a gemini doesn't give him the right to string you along or be neglectful of you. I think gemini's get a bad rap, but some of them are honestly just ridiculous people. Him trying to claim his "mind is separate from his emotions" would be a huge red flag for me regardless of his astrological sign, sounds like a case of denial of his emotions that wouldn't be worth dealing with, especially for a sensitive scorpio