Hey emily,
That's a hard story to read. very sad.
firstly, dating is such a pressure in the teens and 20s. I didn't have my first until i was 26 as well!
secondly, i think from your explanation of his actions, he probably discovered your secret. All in all, it's probably a good thing he broke it off before you had to go through the anguish of explaining and then having to face his reaction, which now, would seem highly negative.
Anyways, be safe. I think it's too dangerous to date men who don't know about t-ism. But that's just the pessimist in me.