Kenny Goss flushed George Michael's drugs down the toilet in the hope he would beat his addiction.
The 58-year-old dated the late Careless Whisper star between 1996 and 2011 and desperately tried to stop the singer from taking the substances by getting rid of them.
He said: "I would find drugs and flush everything down the toilet, thinking, 'If I just get rid of it, he won't get more'. He was absent-minded, so would just think he'd lost them.
"I don't think George necessarily thought he'd die young, but every time I looked into his eyes I thought, 'My God I'm losing you, what is going on.'"
When the pair first met, George only smoked a small amount of dope but Kenny insists he never saw the singer take "hardcore drugs"
He added: "That was a gateway drug to the others. But it escalated. At one point he was smoking 25 joints a day. I saw him smoke weed all the time but never hardcore drugs.
"I heavily disapproved so he wouldn't be around me in that state. He shielded me and his family. He had another group of friends he'd do that with ... When I confronted him, he never denied it, never apologised. He was hard on me about drinking, because I developed a problem."
And Kenny wishes the pair would have "both been able to clean up" and had never split.
He shared: "Of course I wish we'd never split up. But things would have had to change or we would both be dead. I wish we'd both been able to clean up. I started to have a drink problem at about 50. I couldn't sleep, I drank to sleep, that's when it all started. It fell apart.
"George would text saying he wished we were together still – like in the beginning. Our psychiatrist encouraged us to stay together even though it was a dysfunctional relationship. I asked him if I should leave George and he looked me in the eye and said, 'I think you are the only reason George stays alive.'"
The pair would have arguments, just like any other couple, but Kenny says it was only ever over "stupid things".
He told The Sun on Sunday newspaper: "It wasn't perfect. It was over stupid things – who was putting out the bins, losing the remote control was a big one. He thought that I wasn't tidy enough. I thought that he wasn't.
"Luckily we had two housekeepers. They tidied the house. We had a bedroom each, in every single house. Gay guys need more space and their own TV. We'd go to my bedroom for a cuddle, then he would go to his for a sleep."