Most Helpful Guy
He felt by saying what he did, he was letting you down easy and you would be more forgiving of yourself for losing him, not wondering what you did or said to push him away. Unfortunately, that's one of the oldest excuses in the book.
As soon as I read he "wasn't in a good place" and "needed to focus on school" I knew he was full of bullshit. When you are interested and love someone, you make time for them because you want to.
Try not to let it bother you since you now know he's a liar and may have been cheating on you with this woman. And I"m not sure he'll marry this girl, as what's to suggest he's all of a sudden going to change his behavior and not go for the next thing he thinks is better?
We have built in mechanisms to try and protect people from what we deem as very painful, but mostly it's us saying crap to avoid the potential backlash from telling the truth. He figured you'd get angry and blow up in his face, felt guilty and wanted to wash his hands of his relationship with you, so he chose the path of least resistance. You know, "It's not you, it's me".
I've been on the receiving end of this kind of break up and I assumed that person was full of it as well, but in the end, they're done and have made their decision, so there's nothing you or I can do about their desire to move on.
There's a chance he could come back if'/when his relationship fails, but I hope you have the presence of mind to tell you you'd love to, but you've got to study for your board game with family, because Monopoly is so time consuming and your brother always gets Boardwalk! Or just tell him some other ridiculous shit about being Soooooo busy.