ABC News July 11, 2014

Khloe Kardashian Opens Up About Ex Lamar Odom's Cheating

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TV personality Khloe Kardashian arrives at The Hollywood Reporter's 22nd Annual Women In Entertainment Breakfast at Beverly Hills Hotel on December 11, 2013 in Beverly Hills, California.

While cleaning out for her move to her new home, Khloe Kardashian, 30, has a candid conversation with big sister Kourtney and reveals some shocking news in a new clip for Sunday's "Keeping Up with the Kardashians."

She says her ex cheated on her while they were married, the clip on E! News reveals.

Read: Khloe Kardashian Compares Kim Kardashian to Marcia Brady

After Khloe says Odom has been wearing his wedding ring full-time, even though she already filed for divorce, she says "F--- your ring, you were wearing it when you were f---ing someone else too."

She added that Odom was saying "being married to me were the best years of his life," even though she couldn't reach him for months at a time.

"He doesn't think we are going through with the divorce," she adds. "I'll always be his wife and he'll never call me anything else. Whatever, now he's finally admitting he's done f---ed up s---."

She continued, "Let me tell you something. Last year on my birthday I lied to everyone because I had to lie and say I was with my husband when in fact my husband was missing with another girl!"