My boyfriend of two and a half years is acting weird. What should I do?

The toughest part of a relationship is between 3 months and 3 years. That is usually when the breaking up happens. I think that first, you should give him space. Don't text him, don't call him, don't email him, whatever, don't do it. Let him start to miss you. If you're always there he's not going to know what he's missing when you're gone. Don't show him much affection, like saying "I love you" or complimenting him or anything. Don't invite him to hang out, kind of play hard to get like at the beginning stages of a relationship. If he starts to change his behavior you'll know he just needed space, but if he just starts to fade out of your life like he couldn't care less that you're not there then you should break up with him. Because you've been together for quite a while, I would not give up so suddenly though. You could also try talking to him and asking why he keeps cancelling plans.