As Fergie once sang, big girls don't cry.

Nine months into her marriage to Josh Duhamel, the Life As We Know It actor was accused of sleeping with Atlanta stripper Nicole Forrester in 2009. Though Duhamel, 39, publicly denied cheating on his wife, Fergie has said little about the incident -- until now.

Appearing on the October 21 episode of Oprah's Next Chapter, the 37-year-old admits "it was difficult" when reports of infidelity on her husband's behalf first surfaced.

"When you go through difficult times, it really makes you stronger as a unit, as a partnership. It does for us, anyways. Our love today is a deeper love, definitely," the Black Eyed Peas singer vows. "We're stronger today definitely because of anything difficult that's happened with us. We deal with it, we communicate; communicating's the most important thing."

Together for nine years, Duhamel assures host Oprah Winfrey, 58, their bond is unbreakable. "We've both had to work for what we got. We're both Catholic. There were a lot of things that were really compatible between us," the actor says. "But at the end of the day, she's just an amazing girl."

Oprah's Next Chapter airs Sunday, October 21, at 9 p.m. EST on OWN.