A drug confession and an ugly concert incident could plunge country music superstars TIM McGRAW and FAITH HILL into a $140 million dirty divorce!

With their 18-year marriage hanging by a thread, sources told The National ENQUIRER Faith “is reeling” from an interview her 47-year-old bad boy hubby gave in which he admitted past drug use.

Tim – who claims he’s been clean and sober since 2008 – said of his wild past:

“I drank too much, partied too much. And did other things too much. Chemically.

“No needles or that kind of stuff…use your imagination,” he said.

The comments prompted insiders to say Tim was referring to partying when cocaine use was rife in Nashville.

After furious clashes and suspected infidelities, a source told us in March: “Faith finally put her foot down and told Tim he had to straighten up or their marriage was over.”

We also reported that Tim snapped, “I’m treated like a dog!”

But the marriage took a hit in July when Tim became infuriated with a married female fan at an Atlanta concert and slapped the woman in an incident caught on video.

In an exclusive interview with RadarOnline, Tim’s “other woman” Jesslyn Taylor said: “He bent down to sing to me. I reached up … two of my fingers got stuck in his jeans. When he turned to walk away, it ripped a hole.

“He slapped my hand away. Then he turned back and slapped me in the head very hard and I fell backwards.”

Jesslyn was humiliated and Tim eventually made amends with the woman.

Tim and Faith, meanwhile, seemed at odds at a Sept. 16 concert, an eyewitness said: “Their chemistry together seems gone.”