I'm going through something some what similar. Been living w gf for a yr and a half. Some desires have changed and gf now saying I cannot have any sexual contact in our house what so ever, even in my own room. We did not discuss this before moving in together bc were not aware it would become a desire, so we're in a little different spot than you. For my gf, she says she won't ever be okay with me getting what I want in that sense. So it's something we have to think about...
I think it's normal for you to feel uncomfy and you don't have to love the idea of them having sex in your house. They would be kind to get a hotel until you warm up to her. I do think it's something you may want to work on accepting, since you knew your partner was poly all along, this is something to be expected. He should give you time, but I do think it's important to come to a compromise eventually. Of course it is your home and if you don't like something you shouldn't have to put up with it. It's just a matter of what causes less conflict and more connection.