CJ de Mooi contracted HIV while homeless aged 18 when he had to resort to prostitution to "stay alive".
The 49-year-old former "Eggheads" star told fans earlier this week that he has been "living with AIDS" for the past 30 years, and has now revealed how he contracted the virus - for which there is no cure - and admitted he is getting "more and more ill every day" after "constant stress" has "weakened" his immune system.
He said: "I contracted HIV when I was 18 because I was sleeping on the streets.
"I had to resort to prostitution just in order to stay alive. I'm not ashamed of that, I did it because I wanted to live.
"This has been a situation that I've been living with now for 30 years. With the current medication, the situation is manageable.
"I went to the hospital and I was stable. I've been given a course of new medication. Over the last three years, I've had a lot of issues, shall we say?
"The constant stress of everything that's been going on, has, according to my doctor, weakened my immune system so much that it's now very vulnerable.
"I'm getting more and more ill every day."
CJ has had a turbulent time of late after he was axed from "Eggheads" in 2016 over a wrongful accusation of sexual assault, and he has racked up huge legal bills fighting extradition to the Netherlands after being accused of manslaughter, murder, assault and battery in Amsterdam in 1988.
The pro quizzer - who lives in Caldicot, Monmouthshire, with his husband Andrew Doran - doesn't know "how long" he has left but doesn't want sympathy from anyone.
Speaking on talkRADIO, he added: "I don't want people to feel sorry for me, especially about my health. I don't know how long I've got left."