Publicly, Ellen DeGeneres and Portia de Rossi's marriage looks picture perfect, but behind closed doors, it's a completely different story.

The couple is fighting nonstop, and sources reveal exclusively to Life & Style that Portia's insecurity over Ellen's flirty friendships with celebrities is a big reason the relationship is on the rocks.

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Even though it's purely innocent, the Arrested Development star can't help but feel jealous when the talk show flirts with other actresses.

"Portia is convinced that Ellen has so many friendships with sexy movie stars to get under her skin,” says the insider. “She thinks Ellen does it on purpose to make her feel insecure so she doesn’t leave.”

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The tension between the couple, who have been married for nearly nine years, was visible when Ellen and Portia stopped by Craig’s restaurant in West Hollywood recently.

"Ellen seemed miserable and Portia just looked sad,” says one patron. "‘Happy’ isn’t the first word I would use to describe them,” adds a Craig’s staffer.

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Last month, Life & Style reported that Ellen and Portia would get into heated arguments in front of her talk show staff and started a going to therapy together.

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"Ellen hates that. She never wants people at work to know about her personal problems,” the source said. “It was a huge wake-up call for her.”

The insider continued, “Ellen has been in counseling, both solo and with Portia. Part of their therapy is to go on more date nights. That’s why they’ve been seen out and about more together lately.”

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However, the pair continues to deny divorce rumors.

"We're just really good friends and we talk about everything, and we never ever, ever lie to each other, like, not even the tiniest lies," Portia told ET last year. "And she's the only person I want to hang out with. Like, she is my best friend and I just want to be with her all the time."

For more exclusive celebrity news, be sure to pick up the latest issue of Life & Style magazine, on newsstands now. For a look back at Ellen and Portia in happier times, check out the gallery below!