I work for a global company, but the working language is English, so I can expect everyone to speak English. One of the things I love about working here is that I can walk down the corridor and hear all sorts of languages being spoken.
However, if the conversation is to involve me, it needs to be in English. I do have a basic level of understanding in a number of languages, and I can usually get by if I absolutely have to, but I'm far from fluent in any of them, and conversation would be very stilted, not least because I can understand more than I can say. Colleagues do sometimes slip into German or Dutch or whatever, but they don't do it deliberately - they've even addressed me in Dutch before, usually forgetting, and I just mention I'm still not quite fluent (I've never learnt any Dutch at all,) and they just apologise and go back to English. If I were actually based over there, would learn it, because it would just annoy me to live with a language I couldn't follow.
The key point is that it's not deliberate, and they change when it's pointed out. If they didn't, that would be a problem. How aware are your colleagues of how you feel? If it's never been pointed out, it could be they think you're very self-contained and prefer to keep yourself to yourself, rather than realising you feel isolated because of the language. If it's deliberate and conscious, it's basically bullying. Either way, after so long, you probably need some management involvement to improve things, and how they do that would depend on how aware your colleagues are, whether it's awareness and consideration which needs improving, or stamping out deliberate bullying.