Although well-read, the 49-year-old had never bothered to find out more about Aids and other sexually transmitted diseases because he was celibate.
That lack of curiosity is something he now regrets deeply.
'I wish I had known about PEP. I could have been HIV-free now, even if I cannot erase what happened to me,' he told The Sunday Times.
He said he had contracted the virus after being raped during a trip to Taiwan in March this year.
He had hired a guide from the Internet to show him the scenic sights of Hua Lian, known for its mountains and hot springs.
The guide turned up at the hotel the evening before the tour to discuss the itinerary. They chatted over canned orange juice from the mini bar in his room before Bill went into the bathroom to freshen up for dinner.
The next thing he knew, he was lying naked - three hours later - on his bed. There were blood and semen on the sheets as well as in the toilet bowl when he used the bathroom. He suspected the guide of spiking his drink before raping him.
Lost, frightened and ashamed, he decided to bury the episode.
'I blamed myself for being so trusting. I felt that no one would believe me if I said that I had been raped,' said the tall, handsome man who started abstaining from sex a few years ago after a few failed relationships with women and struggles with his sexual identity.
He did not see a doctor upon returning to Singapore. Six weeks later, however, he experienced a deep pain and bleeding from his anus.
He went to a polyclinic where he told his story. Uneasy that the next consultation was a month later, he went to a GP who referred him right away to the Department of Sexually Transmitted Infections Control (DSC).
A series of tests found him HIV positive. There were also lesions on his anal wall and he had anal warts, gonorrhoea and chlamydia too.
Blinking back tears, the devout Buddhist said: 'Imagine - from having no sex to getting everything at one go.'
He added: 'I have been responsible all along. I have not hurt anyone, only myself, by keeping quiet and not seeking help earlier.'
He is currently undergoing counselling and more tests to ascertain the degree of his infections.
'I must remain positive and build up my immunity,' said Bill.
'This is lifelong and I must be strong.'
Braema Mathi