He claims to help up to eight people a week and as many as 20 women could currently be carrying the children.
To date, he has at least 70 known children but believes there could be well over 100 as many recipients don't report successful pregnancies to them.
Matt, who works in IT, said: "With every successful pregnancy it's incredibly rewarding, I've helped couples with fertility issues and those in gay marriages to have the dream they would never otherwise be able to have.
"My sister, who recently turned 43, didn't try to have kids until it was way too late, so she never had any children.
"She thinks what I do is great, in essence I've made up for the fact that she didn't have children.
"All my donations are for free, I'm looking to help people and not to make money off anyone, financially I'm very happy.
"Sperm banks are incredibly expensive and I don't think they always have the couple's best interests at heart.
"I feel the reproductive medical companies find situations where people have to pay more and more for a chance to become parents, which is really unfair."
Matt says his clientele breaks down into: 90 per cent lesbian couples, 5 per cent straight couples and 5 per cent single females, and he is overwhelmed by people seeking his services.
"Currently, there could be between 10 to 20 people carrying the children," he said.
"I have 70 guaranteed conceptions, but I could have up to a third more, it's usually a one-off interaction and you don't always hear anything more from them so I could have many more children.
"I have a fairly strong success rate of helping people conceive, the majority of the people contact me because they know I'm in high demand, I'm donating to multiple people a week.
"Once I donated to four people in two days and three fell pregnant."
"Often I get contacted by as many as 10 people per day, so I try to systematically filter down who I work with.
"I've only met one of the children, I keep things mainly online and feel that me being involved would create a confusion.
"I keep my distance, as I don't want the children to see me as an absentee father, the child's parents are their parents in my eyes."
Matt's recipients must first pass his questionnaire.
Matt said: "I care a lot about the wellbeing of the future children and screen the parents, I don't want to see the offspring in bad situations.
"When screening, I look to see if there has been negativity in their lives, if they have complaints about their relationship, if they're employed, if it looks like they have a healthy, stable home-life and their age."
Matt says his most commonly chosen service is artificial insemination but does also offer natural conceptions as long as the individual provides clear STI tests.
He added: "The large reason people go with me is I'm pretty successful in helping people to get pregnant and I have a good manner of professionalism.
"I'm fairly fit, I do cross-fit a couple of times a week, fencing and a lot of swimming, I used to be a lifeguard too.
"I have an advanced degree in business, no health problems or genetic history of heart problems in the family."
Matt, who is a single father-of-two, hopes to have more kids of his own in future and says eventually as he gets older he'll leave his secret sperm donating life behind him.
Matt said: "I'll keeping doing this until I'm 45.
"A lot of couples come back to me for second children, so I figure when I hit that age I'll have to stop accepting new people."
