Thanks for your reply! I lost track of the forum for a while but now I see your post

Well, we talked about it. It went ok, but he was not too fond about me going. He didn't want to talk about it a lot. I tried the preparing part and that seemed to work.
But two weeks later he asked when I was gonna book the trip, I told him me and my friend are waiting cos we want to see the who else will book the trip on a specific date.
I wasn't prepared for his reaction; he got very mad cos I didn't told him about other people joining. And he is completely anxious and angry maybe other men will join and try to get involved with me.
I know I haven't said it that specific it is a group trip, but I even asked him whether he wanted to do a private trip in 2018 or a group trip. But now he says there is no way he could have known it was a group trip.
I can try to fight his argument, but I know its his version of the truth (the truth he wants to see). He never was interested in talking about my holidays so how could we have spoken about it.
Anyway, I tried validating, saying I understand his feelings. But also said we are together for 1.5 years, I love him, and that his thought of me being interested in other men is only based on irrational feelings of himself. And by saying it that way, he makes it sound like I am some kind of girl who will just have sex with random men it makes me sad.
So we argued about 10 minutes. Then I got quiet. I did not know how to end this conversation. Went to bed alone and angry. Next day he asked if we could forget about it.
But now what... .? when I'll book my trip this argue will be brought up again. It's a circular argument and I do not know how to react.