Grammy Award-winning singer Gladys Knight says her gambling compulsion has gotten so bad at times that she's spent more than $20,000 on a single hand.

"You're numb at that time to what money is," the recovering high roller confesses to interviewer Harry Smith on Monday's A&E Biography Close-Up: You Want to Bet? (8 pm/ET). "Especially playing with those little chips. When you're clicking those chips, you're not thinking dollars."

Knight, who rose to fame with backup singers The Pips on their hit collaboration "Midnight Train to Georgia," says she first realized she had a serious problem when gambling in the casino began to take precedent over picking up her son from school. Eventually, she found herself in the casino plunking down chips around the clock.

"I used to get up at 1 o'clock in the morning, 2 o'clock in the morning after everybody's sleeping and go to the casino," says the longtime Las Vegas resident. "And when my mom realized that I was sick, she used to just cry."

It was after one particularly big gambling spree that Knight, feeling nauseous and shaken, went directly from the casino to a pay phone and contacted Gamblers Anonymous. "I told them who I was and I said 'I'm sick and I need help,' " she says. "And my sponsor at the time, she didn't ask me no questions. She said, 'Where are you?' And I told her where I was. She said, 'You stay right there. I'm coming to get you.' "