So my boyfriend and I are both college students but at different colleges. We had planned a short road trip over spring break. I was really excited for this and was sending him pictures of the thing we were going to go do/see. We were also going to pick something up in a city. (this is relevant later, I hope.) 
Last night he messaged me asking if it would be okay if we dont do the trip and he does a very similar trip with a friend of ours. His reasoning is that our friend does not have a ride to get home from his college (different from the one that I or my boyfriend goes to) and if they do the trip together my boyfriend would be able to give him a ride home and pick up the thing he needed all in one fell swoop. The three of us cannot go together because we have a two person car.
I am pissed off that he even thought it would be okay to ask. I have expressed to him many times before that I have when people are flaky or when plans change in general. So like IN WHAT WORLD would I be okay if he takes a vacation that I suggested without me and with our friend. His argument is that he was just asking and he is fine if we stick to the original plan. I feel like the fact that he even considered ditching me is a dick move. However, he seems to not really get that me made me feel like I'm less of a priority to him than his friend. It might be relevant that the friend apparently has no other way home for spring break than catching a ride with my boyfriend, though I think he could take the train or get a rideshare. Is he the asshole for asking or am I the asshole/overreacting to his suggestion?