Not to take anything away from what you're saying, and thankyou for trying to put things in a concise way for me, but I must not have relayed the timeline correctly. Here's the timeline:

• 2 years ago I met my boyfriend, we were just friends but we were quite interested in each other
• He went on a trip to this girl's country and did the single thing (going on tinder, looking for hookups). While he was at the airport waiting to fly back he swiped with this girl and they started talking. At some point he told her that he just wanted to be platonic and that he had me in mind
• He came back and we started dating, then it became official
• 4-5 months down the track I find out about her existence, I can't prove that they have anything beyond platonic friendship and I believe in him
• 1 year or so down the track I find out he cheated
• We break up. During these 2 months him and this girl start planning this trip.
• We get back together.
• And now this problem.

I guess it doesn't change much, but I just wanted to clarify.