Sarah Aspin, who has a 15-month-old son with Blake, says she found the 30-year-old choking in bed following an afternoon drinking session with a friend.
He was rushed to hospital suffering from multiple organ failure, where he remains in a critical condition.
Aspin told The Sun: 'Blake had a 1pm appointment with the probation service in Morley and said he might be late as he was meeting a friend.
'He's never really been a drinker, but when he got home with this friend, he was slurring his words and staggering — I thought he was on something. I was very angry because he'd been doing so well.
'I had to get his shoes and trousers off to help him into bed.
'Next morning I went to get up and heard a horrid scratching and grating breathing sound. I looked round and saw Blake lying there completely grey.
'His eyes were rolled back and his mouth was locked together.'
Blake had swallowed his tongue and choked on his vomit, with paramedics inserting a tube into his throat to enable him to breathe.
Doctors have warned Aspin they cannot rule out permanent brain damage.
'The doctors say they don't know the prognosis,' she said.
'They said they put him in a coma to help him and due to infection.
'I'm praying he’ll survive, but I'm having to prepare myself that he may never wake up.'
Aspin says the pair, who met in rehab, had been discussing marriage just days before he was rushed to hospital.
Blake, who has battled heroin addiction for years, married Amy Winehouse in 2007 before the pair divorced two years later.
Blake has been widely blamed for introducing Amy to drugs, although father Mitch Winehouse said last year: 'He started her off on the road to drugs. But I don't blame him for her death.'
Today he urged fans to pray for Blake, writing on Twitter: 'Terrible news about Blake this morning. Remember Amy loved him. Let's pray for his recovery. Mitch.'
At the time of Amy's death in July last year Blake was in prison after being jailed for burglary and possession of an imitation firearm.
He was released two weeks ago, days after the one year anniversary of the singer's death from alcohol poison
