Khloe Kardashian Opens Up About Ex Lamar Odom's Cheating

— -- 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!"