I bet you're accent has changed enough that when you're back in the US people ask you where you're from, and if you want to avoid it you have to "do" an American accent. It's tough being a perpetual foreigner, man without a country, etc.
This sense of displacement will be magnified if your personal relationships are few or weak. I agree a series of casual sexual encounters won't sooth very effectively. It may be time for you to decide on a place to live. Plant some roots, have a serious relationship, find some friends rather then passing acquaintances, etc. I don't know you too well D, but that's some of the stuff I've struggled with.