This doesn't sound good!

Ellen Degeneres and wife Portia DeRossi are in couple's therapy following the Australian actress' rehab stint at Passages Malibu in May. The reason? The Arrested Development star believes the talk show host cheated on her!

"[Portia] thinks she had an affair with one of their mutual friends right before Portia's rehab stint in May," a source tells In Touch.

The daytime darling doesn't want to give up on the marriage, so she's trying to win back Portia's trust one day at a time.

"It's going to take a lot for Portia to trust Ellen again. They kept up with the therapy after Portia got out of rehab, but they still have a long way to go," the source adds.

We thought they were one of the most solid couples in Hollywood, but we guess everyone has problems!