I noticed you mentioned you don't feel like yourself in your current social situation, are you adapting your thoughts and opinions to suit others when you're having conversations with them? If so, don't do that. I'm a weird alt/goth person who is severely opinionated, while I could work on being less crotchety, I try not to censor myself. I tried to fit in once, it felt horrible, now I'm just me and people can take it or leave it. If someone doesn't like you for you (provided you're not acting like a jerk) then to hell with them.
That being said, if you aren't trying to change yourself to suit other people's needs, I think what you're experiencing could just be the discomfort of trying to be social when you're not accustom to it. Going abroad is new and awkward, meeting new people is inherently awkward for just about everybody. This discomfort will pass in time, don't beat yourself up about it. I think everybody feels like an outsider when it comes to already established friendships, especially when those people have a lengthy history full of inside jokes. I remember once laughing at somebody else's inside joke because I thought they were just being silly and they immediately reprimanded me for not knowing what it was about. It can be difficult to fit into an already established relationship, so don't try, focus on them as individuals, see if you really connect with them, maybe you'll only be compatible with one over the other. Try to enjoy the process, it can be fun learning about other people. If it's not then you're probably not actually interested in them and that's fine. Sometimes a casual business like acquaintance is good enough to fill the gaps while you wait for something more substantial to come along.