The first time my boyfriend, Sam, slept with someone else, I was intrigued. “What was it like?” I asked. He sighed: “Fine.” I had so many questions: where, who, what did she look like, but he refused to answer any more when I asked about her knickers. (“I’m just wondering if they were nice?” I said. “Like, standard M&S or Rosie for Autograph M&S?”).

Sam and I have been together for almost a year now, and I don’t think he took me seriously when I first, briefly, mentioned that perhaps monogamy wasn’t for me (“I thought it was just one of your affectations,” he said). But as time has worn on, we’ve butted up against my resolve like rubber ducks against an iceberg. “I feel like you’re doing it because it’s…” he looks disgusted… “trendy.”

Non-monogamy seems to be having a moment. An umbrella term, it encompasses the range of relationship configurations that can come about if you decide that “one for life” isn’t quite for you.

“We’re finally rejecting old binaries,” says the comedian Rosie Wilby, author of Is Monogamy Dead? “As we think in a more sophisticated way about gender and gender identity, and about sexuality, it’s natural that we’ve also begun to question the structure of our relationships. All those conversations feed into one another.”

I’ve never been a hardline monogamist. In my last (monogamous) relationship, I always contended that if my partner slept with someone else, it wouldn’t necessarily mean that it was, y’know, done. It seemed reductive to boil down the suppers, red-wine-stained kisses, whispered secrets, adventures and grievances and confidences we shared, the sheer everything of a relationship, to a shag. If our relationship existed on so many levels – friends, teammates, confidantes, lovers – then it couldn’t be undone by one act; and that’s quite a noble thought, isn’t it?

Polyamory has been getting a lot of press. It basically means having concurrent relationships with more than one person. You might have one primary, but everyone you choose to be with is more or less equal in your affections. My preferred configuration isn’t actually that radical: ethical non-monogamy is basically a good old-fashioned open relationship. There would only ever be two of us in it, but I’d like to trust that person so implicitly, and value them so wholeheartedly, that if they slept with someone else it wouldn’t damage us. I’d like for the other person to trust and value me just as much so that if I did the same, we’d be able to look at it for what it is: a banal act that is fun or weird or intimate or exciting, but ultimately not a threat to our harmony.

“A sort of flexitarian approach to relationships,” I said to Sam. “You have a primary partner, and they’re the important one… ” He rolled his eyes, and I told him he was being too middle class about it. “Me just wanting a normal relationship, where you don’t sleep with other people? I’m not sure that’s quite Volvo territory,” he replied.

Finally, he admitted to me: “Maybe because of the traditional expectations that are put on men, it’s more difficult for us to be open about it. There’s something a bit embarrassing about the woman you’re dating wanting to sleep with other people; as if maybe you’re inadequate.”

I was soon put to the test when Sam failed to meet me one night and went home with another woman

Earlier this year we’d reached something of an impasse, so I took Sam to a talk that Wilby was giving above a pub in London. Soon enough, we were packed in with 83 others – mainly slightly older couples and groups of female friends.

“It’s quite a scary concept,” Wilby said. “Because we don’t like the idea of our partner being with someone else. But generally, it’s because we’ve been taught to believe this means that our partner will leave us. Of course,” she continued, “the key point of non-monogamy is that even though your partner might be with another lover, they’re actually coming back to you. And that extra joy and love and happiness might even fuel and rekindle the relationship they have with you. We’ve been conditioned to believe other people are a threat to our relationships, but what if they aren’t?”

I soon put this to the test, when Sam failed to meet me one night as promised and instead went home with another woman. I felt perturbed: “But you said you might come and meet me.”

He sighed. “Am I meant to apologise? You said it was fine as long as we’re honest.”

I sat sulkily for a while. “Well as long as you had fun, Sam.”

A little scab developed over the wound of not being chosen over a nameless woman in a shitty bar. Still, I eventually wriggled into a comfortable emotional spot about this one, too. “I’m totally fine about it now,” I said a few weeks later.

The truth is, of course, that it’s incredibly tricky, and not something you can just foist on someone if they’re not keen. As Wilby points out, though: “Having the conversation, instead of just tacitly accepting monogamy as the only option, is really half the battle.” And we have had the conversation, over and over with each other, but also with others – incredulous friends who can’t quite believe that it’s “a thing”. We field the questions in turn: no, it’s not perfect; yes, we do row sometimes; yes, there are rules; no, we don’t know how long it’ll last. But it is “a thing” – although, after almost a year together, not in the way that I thought it would be. Sam has slept with more people than I have. Despite pushing for it, when the opportunities have arisen I’ve found it oddly difficult to switch into the necessary head space. There’s still a faint feeling of betrayal; and I wonder whether the deed will be worth the emotional cost. More often than not, I realise it won’t be. I’m not sure he feels it in quite the same way. And, yes, sometimes I get tense and irritable when we sit down to eat and he’s too tired to talk because he spent half the night with someone else.

Still, I prefer it this way. We can be really, brutally honest with one another without the fear of damaging our relationship. As far as I’m concerned, hardline monogamy is a recipe for disappointment, because even if you manage it (according to a poll by YouGov about one in five of us has had an affair, and a third of us consider it), there will always be a part of you – that bit that has crushes on colleagues, and fantasises about handsome strangers – that your partner cannot share. There will always be secrets.

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To me, ethical non-monogamy isn’t about sex, or rather, not just about sex; to me, it’s more about radical compassion – accepting that if you plan to spend a lifetime together, you or your partner or both of you will have those urges and fantasies, but, despite that, you’ll be there for each other. You’ll love each other, no matter who or what else comes along.

Back in the pub, towards the end of Wilby’s talk, we learned about relationship anarchy; a woman in the audience was trying it out. A relationship anarchist rejects any rules or constraints, they have multiple partners but no one is more important than another, and sexual, romantic or platonic relationships are all given equal weight. Basically, different partners respond to different needs. “If me and my best friend don’t fit sexually, but know that we’d make great co-parents, then why shouldn’t that be OK?” asked the woman. Six months on, I’m still quite taken with this idea.

Maybe we should just burn them all down, these narrow streets that we’ve paved so that our desires move in straight lines. I have grieved, really grieved, over the loss of old relationships. I think of the heartbreak when Wilby says, “One of the key issues with the traditional format of exclusive, romantic relationships is that there’s an assumption that unless it lasts for ever, it is a failed relationship – when it might have been good for 10 or 20 years, when it might still be good, but for a change in one element.”

Maybe it’s not committed relationships that non-monogamists are rejecting, but the idea that those relationships have to end when the romantic part does. And isn’t that desire – to keep those crucial people in your life – deeply romantic in its own way?

Non-monogamy might not be the answer to any of this, but at least it’s asking the question.