I wanted to know what was the matter, and he told me I had been conceived by donor insemination. I remember thinking that teaspoons were somehow involved, because he'd used the phrase medical treatment, and teaspoons were what medicine came on, but I didn't really understand what he meant. I grasped that he wasn't my father, but I didn't understand who was. I remember feeling it was my responsibility to make him feel better though, so I wiped away his tears and said, "Don't worry, I love you and you're the only dad I know."
Throughout my childhood, my family would use phrases such as "donor conception" quite openly, but they never acted as if this meant I had a genetic father, or a different paternal family out there, even as I got older.
I didn't tell friends I was donor-conceived until I was a teenager, and even then I didn't think about what it meant.
By my mid-teens, I felt uncomfortable and confused about who I was, but I didn't have the words to verbalise it all. I started suffering from bulimia and bouts of depression - it was like a cauldron of black stuff that would bubble up every so often - but I couldn't have told you what it was about.
Then, in my early 20s, I happened to attend a conference where adoptees talked about their feelings of "genealogical bewilderment". That night, I had a dream where two fathers appeared. One was talking to me on the phone and the other was looking at me through a hospital glass window. I woke up in a sweat, with heart palpitations. It was as though I suddenly realised that I did have two fathers. I ran to the mirror, grabbed my long hair and put it where a moustache or beard would be to see what he might look like.
I felt huge relief, but I found myself with more and more unanswered questions. What would it be like to look my genetic father in the eyes? What colour were they? Were they gentle? Would I like him and would he like me? I felt incensed about not knowing who my siblings were either. What did we have in common? Were they funny, or tall, or nice?
Around the same time, I started to experience grief and loss at not being related to the dad who raised me. I grieved that I was not Jewish, like him; I was not part of that rich, familiar and beautiful heritage.
Like many adopted people, I wanted to trace my genetic relatives to find out who I really was. But while it's accepted that a lot of adopted people feel this way, I came up against a complete denial about the long-term consequences for those who have been donor-conceived.
A few years after I started looking, some friends rang to say they had seen a man called Dr Beeney on TV. He had written a book, in which he claimed that a small number of medical students from Bart's - now high-profile doctors - had donated sperm time and time again up and down Harley Street. They had treated the clinics as a "wank bank", he said, and he estimated that he and his friends must have fathered between 100 and 300 children each. He had written the book because he had re-evaluated his actions and had been really troubled by the biological and moral consequences of what he had done.
I was shocked. That meant that I could have up to 300 brothers and sisters out there. But I was also incredibly excited, and longed for him to be my father. I contacted him and we both took blood tests. Our blood types were compatible, but when a DNA test came back negative I wept. I was desolate.
Not only was he not my father, but it was dehumanising and deeply upsetting to know that I was bred with plastic gloves, and without any thought or understanding of the long-term significance of my genetic kinship.
In 1998, I went to the high court with a case against the government. I argued that, like adopted people, I should be given access to my genetic identity. Finally, in 2002, my case helped to lead to a ban on anonymity for sperm donors, which came into force in 2005. I would like to have taken it further - to include making it mandatory to state on your birth certificate if you are donor conceived (at the moment unless you're told by your parents - and it is currently estimated that more than 85% are not -your birth certificate gives misleading information). I also wanted to pursue the mandatory safeguarding of our records, which are currently being destroyed, and the retrospective rights of access that adoptees gained in 1975. But after a seven-year battle, I had lost a lot of money.
Beeney is not my father, but I have reason to believe someone else in his group is.
Unfortunately, however, that man threatened legal action when I politely requested access to what could be my medical history. I have not lost hope about meeting some half-siblings, though, especially as there are probably so many of them. In fact, I frequently receive messages from other donor offspring, who send their photos and ask if I look like them.
Given the number of half-siblings I most likely have, I do have concerns that I might wind up having a relationship with one of them unwittingly. I know of other donor offspring who share that worry. In adoption, the issue of genetic sexual attraction is recognised - you are more likely to be attracted to someone you have some genetic commonality with. For us, it's not, despite the fact that so many people do not realise they are donor conceived.
Despite my sense of injustice, I love and am loyal to my family. But it is still a very sensitive and prickly issue, and relationships can feel deeply strained at times. My mum and dad - who are now divorced - have made massive efforts to understand how I feel, but it can still be very difficult. I think that like many people who go through donor insemination, they were naive and deeply focused on themselves and their infertility.
It's not that I don't feel for people who have fertility issues. If people genuinely want to have a child and can't, that is tragic. But on the other hand, should you have a right to access somebody else's reproductive capacity without even knowing them, and with no thought for the identity of the human being who is produced?
Today, UK regulations stipulate that the maximum number of families that can use sperm from the same donor is 10, but this week the British Fertility Society is pushing for more. It says there is a shortage of sperm donors, as if this were a serious public concern. Radical reform of the current system is needed, it says, preferably [the removal of] donor anonymity in light of the fact that currently 35% of potential donors drop out after their first inquiry. But I see this dropout rate as good. I think those men who decide, upon reflection, that it's not for them are to be supported and admired. If you compare donor insemination to giving your child up for adoption, you see it for what it is.
One of the most upsetting things for me about the way I was brought into the world is the blatant double standard involved. My mother's need to have a genetic link to her child was valued, while my need to know, love and understand the father with whom I have a genetic link was not.
• Jo Rose was talking to Kate Hilpern. For information about UK Donor Link call 0113 278 3217 or visit info@ukdonorlink.org.uk