<human>: I'm 18f and my boyfriend, who I've been with for over 2 years, recently turned 21. He was originally going to have his party this Saturday, the 13th. I told him that I could definitely come. I planned to get him something nice to drink, spend the night, and I was really looking forward to it. (Just to clarify - this party was at his house, not at a bar. And he had other underage people there, so my age wasn't a factor in any of these plans.) 

Well, this Monday I picked him up to hang out because it was his actual birthday. On the ride to my house he starts talking about his party, and in an *"oh, by the way"* kind of manner, he informed me plans had changed and he had it that Saturday, the 6th, instead. So obviously I asked him why he hadn't invited me, and he said it was because he didn't think I could come. But he knew I wasn't busy Saturday and I'd already told him I'd be able to attend, yet somehow this is his defense.

After explaining to him how hurt and insulted I was, he *did* apologize. But I'm still not happy with him, and now *he's* upset at *me* for not accepting his excuse. 

I don't really know what to do. I don't want to break up with him, but it's like he doesn't even understand why I'm still upset with him. Sometimes it takes more than a couple of hours to get over when someone you love hurts you. I guess I'm just looking for other people's point of view on the situation. How serious do you think this is, and how should I handle it?

Could you distill the essence of the text into 1-3 sentences?
<bot>: My boyfriend rescheduled his 21st birthday party and didn't bother to invite me to it. Says it's because he thought I couldn't come, but he already knew I could. Don't know what to do.