This is massively unhelpful, of course. Since even if there is a universe for each possible version of your life — the one in which you make a singular marriage, the one in which you’re restless and wild and free, and all the others — you’re trapped in this one; knowing they’re happening, right now, might even make it worse. In this world, the moment you commit yourself to someone or something you change everything that comes afterward, and live inside it, or so it feels. You also reject or ignore the people who might have been better off if you’d chosen differently. Life feels less like a multiverse and more like the kind of endless sacrificial negotiation Jacques Derrida describes in his little book The Gift of Death:

Let us not look for the examples, there would be too many of them, at every step we took. By preferring my work, simply by giving it my time and attention . . . I am perhaps fulfilling my duty. But I am sacrificing and betraying at every moment all my other obligations: my obligations to the other others whom I know or don’t know, the billions of my fellows (without mentioning the animals that are even more other others than my fellows), my fellows who are dying of starvation or sickness. I betray my fidelity or my obligations to other citizens, to those who don’t speak my language and to whom I neither speak nor respond, to each of those who listen or read [and so on] . . . thus also to those I love in private, my own, my family, my sons, each of whom is the only son I sacrifice to the other, every one being sacrificed to every one else in this land of Moriah that is our habitat every second of every day.

While some of what you ask is native to bisexuality and polyamory — to sex and the working out of what you desire — the problem is so deep and so familiar to us all that Derrida calls it “our habitat.” In every moment we want it both ways, even when we decide how to divide our time among family and friends. We feel it tragic to choose among competing and equally valid beliefs in order to live our one singular life. This problem of desire and commitment is, for Derrida, also an ethical question, perhaps the ethical question. The moment we pledge fidelity to another person or people, we make an unethical choice with regard to others.