Willis, who had been a part of the band Busted, was rushed to the The Priory after his fiancée, Emma Griffiths gave him an ultimatum to either clean up or forget marrying her.
Griffiths, who is a presenter, was very furious with Willis when he went back to Winehouse's pad after a night out last month, and was even more upset when she saw the state he was in when he turned up at their North London home.
"He went too far after the night out with Amy. He was so out of it he started swinging at photographers," Mirror.co.uk quoted a source as saying.
"He and Emma are supposed to get married next month and have a massive magazine deal but she told him he needs to sort himself out before she becomes his wife. She made him promise that he would give up drugs and heavy drinking - and she's devastated he broke that promise. But Matt loves Emma and wants to do everything possible to win her back," the source added.
Willis' first visit to The Priory had been in 2005 for alcohol abuse, and then in 2006 he was re-admitted for his addiction to weed, which he was smoking at least a joint a day for eight years.
The singer is not the only one who has landed himself into trouble with Winehouse, last month it was revealed that her timid ex-lover Alex Haines was sacked for alleged drug taking.
Another to have been affected by her was former tour manager Thom Stone, who quit after handing in a doctor's note, which said heroin had got into his blood after he'd been on the road with her.
There have not been any comments from Willis' spokesman as yet.