Am I in the wrong by being upset, or is he in the wrong for not understanding my currently situation and making sacrifices to attempt to make me happy? I just want to know so I can change it, depending on other peoples views.
My dear, you need to find your own happiness and stop relying on your boyfriend to be your everything. That's way to much pressure on one person to make two people happy all of the time.
Before you go to Spain, make a promise to yourself and this board and start a hobby or a class or join a sports team that will allow you to meet new people. I'm sure there is something you've always wanted to do but have never done it. Pick something and make your own fun independently of your boyfriend. When you are happy with yourself then you will not be so upset and angst ridden when you bf isn't with you. You will miss him more in a normal fashion but you won't consider him being gone a "dilemma" and you won't play these "am I right or is he right" games with yourself.
A boyfriend should enhance an already happy you... Not make a sad you, happy.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion