How would you react?

So me and my boyfriend have been together for almost 2 years.. we’ve been doing long distance for a few months now before that we were living together. Halloween is tomorrow and it’s one of my favorite holidays. I’ve been telling him for days how excited I was to see him because it’s been 2 weeks.. I already paid for a dog sitter while I go see him tomorrow but tonight he was saying he needed to cancel and we hangout over the weekend instead. He was acting weird about it so I had him tell me what he didn’t wanna tell me. And it turns out he made plans to go hangout at his friends house with some of his other friends. So basically blew me off to spend it with his friends. As heartbroken as that made me feel I asked him if I could just come along and he said no... I’ve been so hurt and crying these last few hours I just don’t understand. Why wouldn’t he want to see me for halloween? Could he be hiding something?