When I first heard about the HIV-prevention drug PrEP – pre-exposure prophylaxis – I had mixed feelings. The NHS is already at crisis point and cannot afford to pay for certain cancer treatments, so why should it pay for PrEP? Currently, PrEP is only available on the NHS in Scotland and not in England and Wales, and it remains controversial even among readers of the gay magazine Attitude. “Why should my taxes pay for these sluts to have bareback sex?” is a typical comment. But I was worried that my reaction was the result of anti-gay conditioning, being brought up to think that I didn’t deserve the same rights as the rest of society, and I wanted to challenge this by taking the drug for three months to find out more.

I am lucky enough to be able to afford to buy PrEP legally online. Within the EU, PrEP is still under licence from the US pharmaceutical company Gilead Sciences, and the NHS has no choice but to buy the drug from them, under the brand name Truvada, at a cost for each user of £400 per month. I order “generic” PrEP from a Bangkok clinic recommended on iwantprepnow.co.uk. It is priced at about £40 a month and I buy a three-month supply. A few weeks later three boxes of PrEP arrive in the post.

Several sexual health clinics in London and cities such as Manchester, Brighton and Birmingham offer PrEP monitoring services and so before I start taking it, I check that it is safe for me to do so. At the Mortimer Market Centre, part of the Central and North West London Foundation Trust, the staff are friendly and nonjudgmental and the service is excellent. The nurse assigned to me is Abramo Marchesani, who is gender non-binary and prefers female pronouns and the name Amanda.

Amanda tells me that between February 2016 and February 2017, 201 individuals attended their weekly PrEP clinic 327 times. “When we set up this service, we thought that it would be more high-risk men who have sex with men, people who are into the chemsex scene, people with a chaotic lifestyle,” says Amanda. “But for some reason, the people we see are actually men between the ages of 30 and 60, who are quite knowledgable about the risk-taking.”

She chats to me about my own sexual history and how to take PrEP, explaining that there are two options – either a pill every day, which will give protective drug levels continuously, or through event-based dosing, which involves taking PrEP in the run up to exposure to risk. The drug will take up to seven days to get into my system, but if I take a double dose on the first day, I will be protected after just a few days. I decide to take a pill every day.

Like any drug, PrEP can have side effects. Fewer than 10% of people have reported nausea, diarrhoea, bloating and headache. More seriously, in some cases it can impair the function of the kidneys and lead to a slight reduction in bone density. My blood and urine are tested and I undergo a full STI-screening, involving anal and throat swabs. These will be repeated after one month, then at six months, and then once a year. I am also asked to commit to a full STI check once every three months.

It may seem strange that the clinic is allowed to provide the service when the prescription of PrEP has been blocked by the NHS. But, as Laura Waters, the clinic’s consultant physician in HIV and sexual health, points out: “The General Medical Council is very clear that a clinician has a duty to make sure patients are informed of all treatment choices, whether they’re available on the NHS or not.” NHS England will begin a three-year PrEP Impact Trial this summer, involving 10,000 participants at high risk of contracting HIV, while Gilead’s rival drug companies are challenging the company’s efforts to extend its patent until 2020-21 in the European Court.

I leave feeling nothing but admiration for the clinic’s staff, who are willing to work on the fringes of what is legal within the NHS to do what they think is ethically right.

A few days later, I receive a text telling me that my kidney function is normal. I take my first dose of PrEP.

Matt Cain at the Mortimer Market Centre in Soho, London. Photograph: Markus Bidaux

During the course of the next week, I start telling people what I am doing. With the occasional exception, they express disapproval or, at the very least, unease. Several grimace at the news and a few friends tell me they “struggle with” PrEP. At a party, I discuss the subject with a gay man I have known for seven years and feel encouraged when he is supportive. When I ask if he himself is taking PrEP he erupts in anger and asks how I dare suggest such a thing. A few days later, a fellow high-profile LGBT+ journalist texts me to say: “I don’t understand how all these sluts are getting PrEP.” The text includes links to articles about rising STI rates among gay men and stories of men contracting HIV despite being on PrEP. These are impossible to verify but are absolutely terrifying.

None of these reactions makes me change my mind about taking PrEP. And, as my experiment goes on, I find myself becoming increasingly political about the subject.

One argument against PrEP is that it is unnecessary because gay men can protect themselves with condoms. But it is not as simple as this. Crucially, a passive partner in anal sex is under much greater risk of contracting HIV through unprotected sex, and it isn’t him who has to put the condom on. And there are a whole host of reasons why the passive partner may find persuading his partner difficult – such as low self-esteem, thinking he doesn’t deserve him, or will lose him. PrEP frees passive gay men from this tricky and often risky negotiation and offers them the chance to empower and protect themselves.

When gay men have sex without a condom it is demonised as “barebacking”. But when straight people do this, it is just “having sex”. Many straight men have told me that their default setting is to have sex without a condom and that they will only wear one at the insistence of the female partner. One straight man, who is in his 20s and has had sex with dozens of women, tells me he has never worn a condom.

Another argument against PrEP is that it encourages gay men to have condom-less sex and therefore increases exposure to other STIs. But when have we ever opted not to treat one infection just because we cannot treat others? Why does it make sense to choose not to treat a serious virus that affects someone for life just because it doesn’t also protect us against minor infections that are easily treatable? And yes, the NHS cannot afford certain cancer treatments, but it does pay for anti-smoking therapies, gastric bands for overeaters and the contraceptive pill for straight people. Most people agree with the principle of preventative medicine, so why should PrEP be the exception? It is estimated to cost the NHS £360,000 to treat somebody with HIV over the course of their lifetime. Surely it makes better economic sense to offer them PrEP?

I debate all of these arguments with friends who express strong reactions to the news that I am taking PrEP. But what I am not prepared for is the strength of my own reaction to PrEP – when I start to have condom-less sex.

I am not a habitual user of hook-up apps but before I start taking PrEP I create a Grindr profile and mark my HIV status as “Negative”. I monitor the number of approaches I receive and the kind of things people say. When I start on PrEP I do the same, changing my status to: “Negative – on PrEP”. I want to see if there is a difference and if I am bombarded with men asking to have condom-less sex with me. I am not and there is no major difference at all. Although I do have one man saying he wouldn’t come near me as he suspects I’m “barebacking” all over the place and am “riddled” with STIs.

The first time I do have condom-less sex while on PrEP is a one-night stand. I tell the man I am negative and on PrEP; he tells me he is negative but not taking it. He does not seem to care whether we use a condom or not but, telling myself I am protected, I go through with it.

Afterwards, I burst into tears. I feel dirty and guilty, as if I have let myself down. I grew up in the 1980s, when fear of HIV/Aids was at its highest and I had it drilled into me that I always had to wear a condom. Sex without a condom was a bad thing.

But I carry on and, over the next six weeks, date a couple of men. One, an architect, tells me he isn’t put off by the fact that I am taking PrEP but he would prefer to use a condom. He tells me it would feel as if we were rushing into the intimate stages of a trusting relationship to have condom-less sex straightaway; we would be skipping over rules that have been strictly laid out since the onset of HIV/Aids.

Another man I date, an older banker, is very supportive of my decision to take PrEP and thankful that we don’t have to use condoms. We don’t and this time I don’t experience any regret or guilt.

The use of PrEP has split opinion within the gay community. Photograph: Alamy

I am not sure which is the right approach but, as it happens, neither relationship lasts.

By the time I can make my second PrEP monitoring appointment I have been taking the drug for six weeks. Amanda chats to me about how it’s going and asks about my sexual activity and adherence to the drug. The STI tests are repeated and a sample of my blood is taken to check my kidney function – and to test for HIV. I am told that I will receive my results via text within the next seven days, or a phone call if there is a problem.

At the clinic, I ask Laura Waters if she has observed any cases of a patient becoming HIV+ while taking PrEP. “No, not here,” the consultant says. “There were some infections within some of the PrEP studies, but almost all of the cases so far have been when people weren’t taking the PrEP properly or where people have had very early HIV infection at the beginning and it wasn’t picked up on the basic test.”

Has she noticed a rise in the rates of other STIs among gay men accessing the clinic’s PrEP services? “We haven’t looked specifically at STI rates in that small group of people,” she says. “But we do know that in our clinic, as in all clinics according to the Public Health England figures, there has been a steady increase in sexually transmitted infections in men who have sex with men. Is PrEP contributing to that? Probably to a degree it is, but it doesn’t change the fact that they were all going up before people were accessing PrEP.”

What is more likely is that the use of PrEP through sites such as I Want PrEP Now is a major factor in the drop in HIV infection among men who have sex with men. This was reported to be around 40% in London and around a third across England in 2016. This is a significant breakthrough and the first time the rate of infections has dropped since HIV was discovered in the early 80s.

A friend who started taking PrEP at the same time as me but wants to remain anonymous says he associated sex so closely with the threat of death and disease that he became neurotic and was unable to open himself up to a relationship. But since taking PrEP he has been able to use sex to connect with someone on a more intimate level – and he and the first man he had condom-less sex with are now in a relationship. He describes having sex with condoms as like “wearing rubber gloves when you hold hands with someone”. Now, he says, it’s as if his sexuality has been set free.

I receive a phone call from the Mortimer Market Centre. I am told there has been an anomaly in my test results. I panic. Have I exposed myself to a PrEP-resistant strain of HIV, like those I have read about online?

While on the phone I am told that I have not been infected with HIV but my kidney function is dangerously low. I have to discontinue taking PrEP immediately and go back to the clinic for an emergency blood test.

When the results come through a few days later, it seems my kidney function is back to normal. The doctors can’t work out whether there has been a mistake in the lab or if the ibuprofen I was taking to cure a muscle strain, combined with the PrEP, has impaired my kidney function. But it strikes me how easily I could come close to kidney failure – and this makes me realise how important it is for people self-sourcing PrEP online to be monitored by the NHS, just like women taking the contraceptive pill have to have their blood pressure checked regularly.

After a few days break, I restart my course of PrEP with a vow to avoid ibuprofen. Shortly afterwards, I fly to the US. I am interested to see whether PrEP is viewed differently in America, where every gay man with health insurance is offered it by their provider and PrEP is widely believed to be changing the way gay men have sex.

As soon as I log on to Grindr I notice that most people mark their HIV status as “Negative – on PrEP”. In fact, the first thing that happens when I switch on the app is that I receive an advert for PrEP on sale at the high-street pharmacy chain Walgreens.

During the course of my trip I have sex with a few men and condoms are not even mentioned – nor is HIV status discussed. I have no idea whether this is a good or bad thing but it is clear that PrEP has indeed changed things. In the past, I had always been struck by how upfront Americans were about their HIV status – and asking about mine. It seems this is no longer an issue or even a conversation – and the sexual activity I experience is entirely free from fear. The drug is completely normalised and there is no stigma. As I fly back to the UK, I think this is what it should be like at home.

Even in the three months that I have been taking it, PrEP has changed my life in ways I didn’t expect; it has affected me emotionally and politically, as well as physically.

Looking at the bigger picture, there is no denying that the drug is a potential game-changer. If all the gay men who are HIV-negative go on PrEP – and all those who are HIV-positive take the medication that will make their viral load undetectable (meaning they will not pass on the infection) – we will have the power to wipe out this disease. If the NHS offers it everywhere in the UK, and all gay men who are deemed to be at risk start taking it, there can be no slut-shaming. PrEP will become the new normal.

The main emotion this unlocks in me is relief; if I carry on taking PrEP, I will never become HIV+. And in the same way that the contraceptive pill freed so many women from associations between sex and the scandal of an unwanted pregnancy, PrEP can free gay men from linking sex and death. It allows us to have sex how it should be experienced – innocently and joyously. It is perfectly natural and a desire that has always been part of me. I had been robbed of it for more than two decades. So I have come to a decision: I am going to carry on taking PrEP.

This is an edited extract of a piece from this month’s Attitude. Matt Cain is the magazine’s editor in chief.