'Apart from his wife, I'm the only woman Mick's ever been with.'

'Apart from his wife, I'm the only woman Mick's ever been with.' Photo: George Marks / Getty

I met Mick online, and we made arrangements to meet for dinner. He brought a surprise special guest – his son, Connor, then 2. We hugged goodbye afterwards. He kissed my cheek. A week later, he came to see me. We had Italian food and watched YouTube videos for a couple of hours. I kissed him. His lips felt soft, and I liked the way his leg felt against my own as we sat side by side.

"Want to fool around?" I asked. "We can go in the bedroom." It had been 400 days since I last slept with anyone.

I'd had longer dry spells, especially if you count the first 35 years of my life. I lost 136 kilograms, found a guy online, and there went my chances at an immaculate conception. Other men followed.

Apart from his wife, I'm the only woman Mick's ever been with. They started dating at 18, and have been together nearly 15 years. They arrived at polyamory because she didn't want to have the kind of sex he liked, and vice versa. Despite this difference of opinion, they shared too much – and needed one another too much – to simply divorce. They had a child together and a life that worked. Both read the book The Ethical Slut and decided that including other loves would help their marriage rather than harm it.

Mick and I saw each other almost every weekend after that first date. We talk online almost every day. There are times when I think I'd like more, though not necessarily from him. If I were to have someone in my life I lived with or saw every day, he would almost certainly be another man.

Part of our arrangement requires some suspension of disbelief. While I know that we probably won't stay together forever, I find it hard to imagine my life without him. We navigate this boundary through a heady mix of affection, humour and some denial. Denial comes in handy. It lets me enjoy our time together – a day, a weekend, a few hours – without sadness or worry or doubt. Those feelings come later, when I'm alone, or when I wish I wasn't.

I sometimes envy Mick's wife, though not in ways most people imagine. They share an intimacy that lacks the physical dimension I have with him. Her particular sexual interests lay more in the direction of things kids do in junior high, or in S&M that Mick has no interest in pursuing.

I envy her for waking up with him every day. I envy her for her official status.

Mick worries his employer would frown on this part of his personal life. There's no status on Facebook for "in a relationship … with a married guy … but really, it's okay because his wife is good with it".

I met Mick's wife shortly after we began dating. Weirdly, she has the same first name as I do, though she goes by Bex, and I'm always Rebecca. She dates other people, too, though her luck with outside partners hasn't been very good.

There was "S", an S&M partner who thought he'd get better private abuse from her if he treated her badly outside the bedroom. Next came "Monster", whose nickname came from their shared love of horror films. His wife felt jealous of Bex and that relationship ended.

Next came Don. Bex sent him to the airport to pick me up one day. Her son needed to see a doctor, so she had to scramble for backup. Don bragged about all the cars he'd stolen, and told me that he was a great dad who supported his kids (three, each with a different mother) totally, "except with money". Bex dumped him fairly quickly.

I enjoy Bex. She has a unique energy and vulnerability. She and Mick have Connor, the three-year-old with whom I've spent a lot of time. Connor has wildly curly hair that falls down his back in a loose tumble. When he sees me on Skype, he shouts "Beeka, Beeka" and asks where are my kitties. We swim together in the summer. When we spend time at Mick's house, I have my laptop open to some YouTube video or another. We listen to Paul Simon, and I sing along to Loves me Like a Rock for him.

When I met Mick, I'd applied to graduate schools in other states. I didn't want to sleep with creeps from Craig's List, or lie to decent local guys about the chances of a long-term relationship. I searched OKCupid profiles for married guys, and Mick was the first one I wrote to.

He was nine years younger than I, and his wife sounded amazing. We made a date, and it's worked out so far. I thought the G-spot was made up before Mick. I've also never dated a man so effortlessly cheerful and (mostly) functional. Mick installed my car stereo in under 10 minutes. I watched him do it from the passenger seat of my Saturn Ion. He bought the wrong mounting kit, but made do with a multi-tool and the old wiring.

"I've never dated anyone useful before," I told him. He smiled and kissed me, made sure the stereo worked, and drove home to his wife.