None of these. You wouldn't be in a human bed, you'd be sleeping in a bunch of hay somewhere just a few feet from the pile of wood shavings where your centaur pisses.
The living situation with a centaur wouldn't be comfortable, but it'd certainly be stable.
I have a question I need answered before I can choose: would gravity mean the half horse/half centaur stands with all six legs on the ground? I failed centaur physics, so please ELI5 :/
Imagine you little spoon your centaur partner and during your deep slumber they suddenly get up, take a piss, drink some water and go for a midnight walk through the woods. And when you wake up because it's getting cold you're on the back of your horseperson, naked, under the stars in the woods and they're like "ah honey I just didn't want to wake you because of your project at work tomorrow". And you won't start a discussion because then perhaps you'd fight and you would have to walk by yourself back home again in the cold which would take forever. So you cuddle up to your horseperson again and hope they're done soon.