LeAnn Rimes' ex-husband Dean Sheremet details her cheating, blasts Eddie Cibrian

Looks like LeAnn Rimes and her first husband, Dean Sheremet, are not exactly friendly exes.

Sheremet, who was married to Rimes for 7 years before splitting in 2009 after the 32-year-old "How Do I Live" singer had an affair with an also then-married Eddie Cibrian, is now telling all in a lengthy interview with Nat's Next Adventure. The former backup dancer talks in-depth about his marriage with the country superstar, specifically, when it all went wrong. Even before the affair, Sheremet says that there were a lot of "animosities that built up" between the two -- mainly because he claims he was also involved in every aspect of her career.

"I felt like I was never having my needs met so there was fighting," he reveals. "And I was so intertwined in managing her career that I didn't know how to make the distinction between husband and boss, husband and partner, husband and manager... I was husband, father, friend, lover, manager. There were so many hats and I didn't know what hat to wear when."

"Unfortunately, I think the business ended up destroying us," he stresses. "That passion for our marriage wasn't there. The person that I needed to be, the person I should have been, I wasn't. I wasn't the person she came home to and unloaded on. And, then, of course, I was thinking, I haven't done what I've wanted to do in over eight years."

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Still, he was blindsided by her affair with Cibrian, her Northern Lights co-star.

"Never in a million years did I think something like that would have happened," he admits, also sharing that it was he who encouraged Rimes to star in the 2009 Lifetime film in the first place. "The need for me in her life was so strong. There were things she couldn't do without me. She had her own phone but never used it. People would call me to get to her. Everything went through me."

He says he never felt threatened by the 41-year-old CSI: Miami actor, though he admits he's a "good looking guy" and "charming."

"I just remember being like, 'Oh, God, just another one of those Hollywood pretty boys,'" he recalls. "If you're in a room with him, he's probably one of the most charming people you'll ever meet. But I wouldn't trust him as far as I could throw this f**king table. He just felt like one of those guys from the beginning. A total schmoozer. Very Hollywood. I never bought his shtick. But I wasn't worried."

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He remembers the exact moment when he knew the nature of his relationship with Rimes had changed. After he got sick and had to leave the Lifetime TV movieset for a week, he says there was a "huge shift" upon his return.

"There was this bar that everyone hung out at after set and I remember coming down the stairs and seeing the two of them shooting pool together," he recalls. "I could just tell by the body language that everything had changed. She's shooting pool, shooting tequila, in a tight tank, tight jeans, over the knee boots and she's standing across from him, playing with the pool cue. All of a sudden, there was a huge shift. My stomach dropped. I literally felt like I got hit."

"I totally felt foolish," he says about eventually leaving the set for good when the tension became too much. "I felt like this pathetic husband hanging around. I was very aware of how others were looking at me. ... I was like, 'Why am I here? I don't need to be babysitting someone on set.' Even though in my brain, I was like, 'I'm seeing this happening, I should be here and do something.' But I wasn't going to be able to stop anything that happened. And I wasn't doing anyone any good."

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He clearly still has some resentment over the situation.

"The dumbest thing she ever did for her career was divorce me, because we were such a good team. The last hit song she had was when she was with me," he says bluntly, referencing her song "Nothing Better to Do," which they wrote together.

"It's funny, I don't remember seeing that on my SAG screeners that year," he also cracks about Northern Lights.

As for Rimes' controversial turn after their split -- including a VH1 reality show with Cibrian that got canceled after one season and a very public feud with Eddie's ex-wife, Real Housewives of Beverly Hills star Brandi Glanville -- Sheremet says he actually "sympathizes" with her.

"She really lives on the adoration of others. I could be speaking out of turn but this is my perspective," he muses. "She lives and dies on the perception of herself. I sympathize with that cause she's been famous since she was 12 years old so she doesn't know anything else. In L.A., there's the paparazzi and that false sense of success, false security that you're still relevant. If you're in the magazines, then you matter. And that carried over to the divorce. She became even more 'famous.'"

"She's one of the most talented people I've ever met, has the most incredible voice, she's flawless," he adds. "But she got away from doing that and it breaks my heart. She's gone away from what she was put on this earth to do. It's all been at the expense of that. I think she learned a really hard lesson because it didn't pan out the way she wanted it to."

VIDEO: LeAnn Rimes -- 'A Bully Tied to Kill Me'

In January 2013, ET caught up with a similarly candid Rimes, who opened up about infidelity.

Watch below:

LeAnn Rimes Talks Affair With Eddie Cibrian and Ex Dean Sheremet
LeAnn Rimes Talks Affair With Eddie Cibrian and Ex Dean Sheremet