OP here. My boyfriend and I haven't been together for long and as others have pointed out, the problem was that he didn't tell me straight up and I had to find out myself, which just made it look really really bad. He didn't tell me cause he didn't want me to feel bad throughout the whole time he was gone (he admitted he would've felt the same if it were the other way around and probably not talk to me for a while) but he didn't think far enough to come to the conclusion that I'd find out at some point (and probably start wondering why he chose to take his ex on all those trips). Now, apart from all that, he told me he doesn't believe in friendships between men and women as one of them is always looking for more than just that... apparently he only has one girl friend where the exception proves the rule, but that friend isn't his ex he took with him on the trip, so that kinda made me feel uncomfortable with the whole situation too. The fact that she talks about her miserable sex life and asks for advice from him kinda had me on my toes as well.. I've been cheated on in the past and have a hard time trusting someone / maintaining a certain level of trust but we talked about it and he was really sorry and all is good :)