At 41, Jennie Withers found herself single and childless. In July 2006, she appealed for a "co-parent". Here's the extraordinary story of what happened next. Plus, an interview with Europe's most prolific sperm donor

It's almost four years since that article. The one published in this magazine in which I made a direct appeal for someone to father my child. I've just re-read it and cringed again. What was I thinking, being so public about my failed efforts at relationships? It seemed a good idea at the time – I was single and 41 – to take a more pragmatic approach to making a family and explore the possibility of co-parenting a child with someone like-minded. I didn't want to raise a child on my own, and I wanted them to have a real father. Nothing changes if nothing changes, and the piece was certainly one way to state an intention. But I hadn't thought through where it might take me.

When the article appeared, in July 2006, it attracted a huge amount of comment – both critical and supportive. It was interesting to hear from people who'd done a similar thing with varying degrees of success. It was heartbreaking to hear from many women in a similar situation to my own – fortysomething, single, childless, but wanting it to be different. What happened to our generation – the women that were supposed to be able to have it all?

I received several emails and letters expressing interest in assisting me with my project. All of a sudden I was "dating" prospective co-parents rather than potential mates and I was totally in the dark on the etiquette. What to wear? What to talk about/not to talk about? How do I promote my credentials as a desirable mother given I have no track record? How do I assess who would make a good "partner" in the enterprise, let alone a good dad? And how do you get to know someone well enough, quickly enough?

It was fascinating to discover that there were many men who for various reasons were looking to have a child outside the conventional family set-up. It challenged an old idea of mine that men weren't really into children. Some men wanted to be putting baby to bed every night, others were happy with birthdays and Christmas. Not able to envisage how things might pan out, I was open to either.

The grief of giving up the traditional idea of a partner/husband was more intense than I had anticipated. But I was excited by the possibilities that lay ahead: I had publicly stated my desire to have a child, which was curiously thrilling and liberating.

I was lucky enough to meet a couple of great prospective dads – kind, decent, lovable men with whom I felt I could feasibly share a child and a life. We spent time getting to know each other, meeting each other's friends – and in one case, his partner – and discussing logistics. It was, as I anticipated in my original article, a bit like the divorce without the marriage, negotiating how to bring up a child separately. The situation demanded a leap into intimate discussions about values, education, spiritual beliefs, living arrangements, financial responsibility and TV-watching policy. One man was horrified about my idea to raise a baby macrobiotically. I was equally shocked by another man's insistence that McDonald's should feature in every child's diet. At least it meant that all these things were discussed upfront.

And then along came Graeme. I knew him vaguely from yoga. I knew his ex-partner, Mark, better. In fact it was Mark who had initially planted the co-parent seed when he suggested several years ago that I have a child with him, but at that stage I hadn't yet given up on the possibility of true love and happily-ever-after.

Graeme and Mark had separated a year before and I got to know Graeme better during that time. It had crossed my mind that he might be a candidate for my project, but I assumed he would have said as much if he'd been interested. I'd had one too many weird conversations with male friends to risk another rejection. (One high point was a dinner with an old friend – single but with definite potential as a dad – to whom I popped the question as casually as I could. He was so shocked he nearly fell off his chair; our evening ended shortly afterwards and I never heard from him again…)

I had held a lunch party to introduce a prospective dad to some friends, and invited Graeme as a possible romantic match for someone else. Graeme says it was then that he decided to volunteer. All he tells me now is that he simply felt he would be a much better prospect. At dinner later that week we just clicked – and almost immediately agreed to go ahead. He was to be my co-parent and I (rather awkwardly) declined my other options.

Visits to doctors and clinics with a view to getting pregnant is a strange thing to do with someone you don't know very well. And there isn't a box to tick for "co-parents" – "No, he's not 'just' a donor; we're doing this together." We also soon found out that we weren't exactly the ideal baby-making team and that we had some medical obstacles to overcome.

My gynaecologist began advising me to "find another donor" (which felt horrible, especially as Graeme didn't know). We grabbed a weekend in Graeme's busy travel schedule to spend some time together and to visit my sister. It did feel oddly like going away with a date, but by now I was used to things generally being odd. There we were having dinner in the local fish and chip shop, talking about the day and nothing in particular, when Graeme suddenly went very quiet. I could barely hear what he was saying as he muttered that he'd fallen for me.

In hindsight it was obvious – friends had hinted at how fond of me he seemed – but at the time I was totally taken aback. My initial reaction was to panic, as I envisaged all my carefully laid plans dissolving. Graeme didn't fit my idea of what I was looking for in a "real" partner. As far as I was concerned, he was my gay best friend and co-parent, and I was quite liking it that way. "We can't possibly have sex – we're supposed to be having a baby," I wailed to a girlfriend on the phone.

We were due for a clinic appointment later that week. It felt very awkward going through the "gay co-parent" explanation again with the doctors. Things had changed, and I wasn't really sure what the story was any more. Excruciatingly, the doctor needed a semen sample from Graeme that day. I'm not sure which of us found that more awkward.

Graeme was then away for a month, so we both had time to mull things over. When he got back, in February 2007, we decided to make a go of it as a couple. As far as he was concerned it was absolutely the right thing to do, and I was being slow to see it. Oh, the confidence!

We dated in a very old-fashioned way. I was wary of getting involved in anything that wasn't going to be for real. And he was probably nervous as hell about getting involved with a woman for the first time in his life. So we took our time. Then one week I accompanied Graeme on a work trip to Verona. I'd insisted on separate rooms and was full of slightly crazy ideas about writing a formal charter for a relationship (we'd been doing the same for child-rearing). Graeme patiently put up with it all and took me to a beautiful place on a lake for the weekend. I remember skipping down to breakfast one day knowing that he was the man I wanted to share my life with, and writing in the hotel guestbook that this had been the place where we'd fallen in love.

It was a glorious summer. We threw a party and announced our news. I moved to Graeme's and he plucked up the courage to tell his parents ("Surely it can't be harder than telling them you're gay?"). Friends and family were mostly delighted; some friends found it hard to accept. Funny that it seems very acceptable for a man to go from straight to gay but not the other way around. One of my dearest (gay) friends couldn't have been more shocked when I broke the news. "Falling for you? That's just not possible." Hey – thanks.

Graeme was unfazed: he had found someone he loved and spent the first half of his life with them. And now he had found someone else he loved. It was challenging, but it was funny, too – Graeme getting used to women (feminine logic, emotional outbursts and carrying luggage), and me getting used to a man who wasn't used to women.

Romance took over from engineered baby-making for a while. There was, however, little chance of conceiving naturally – and it was a blessing that we already knew that. We decided, a little impulsively, to move to New York. Graeme wanted to leave his old home and make a new home together, and by September 2007 we had found a little apartment in SoHo and were making our life there.

I was still holding out hope that we'd be able to conceive naturally. From macrobiotic remedies to Chinese herbs, acupuncture, bodywork of various kinds, body/mind therapy and a mad clinic in Florida that promised to unblock Fallopian tubes – I think we tried it all. At least we got pretty healthy in the process. We also progressed along the western medical route with IVF. And in February last year I found out I was pregnant.

I won't ever forget leaving a clinic in London after the all-clear on the big test (for Down's syndrome etc). It was a beautiful day. Graeme and I grabbed some lunch in a little café, stunned and happy. Telling friends and family was joyous. Neither of our families was expecting either of us to have children, so it was special news to tell. Friends who'd walked this path with me from the beginning were thrilled.

Victory Alexander was born here in New York on 7 November 2009. We were lucky to be able to have him at home (not many people do in NYC) and we had a wonderful midwife and doula. It truly was the night of my life.

It's been a privilege to spend these past three years with Graeme, who has been as good a man, lover, partner and father as I could have wished for. Perhaps the advantage of having a more pragmatic approach to coupleship, rather than getting too caught up in the romantic love-bubble and its disappointments, is that it feels we are building something solid, healing, and deeply satisfying.

As I sit here listening to Graeme sing songs to his baby son in the bathroom, I am awed and humbled by the mystery of life's twists and turns. Two weeks ago, Graeme asked me to marry him. A perfect end to the story this far.

To read Jennie's original article, go to http://www.theguardian.com/lifeandstyle/2006/jul/02/familyandrelationships