Britney Spears: I Married Kevin Federline "for All the Wrong Reasons"

"I think I married for all the wrong reasons," Spears says, as her hit Womanizer tellingly plays in the background. Watch above.

"Instead of following my heart and, like, doing something that made me really happy," she continues, "I just did it because...for just, like, the idea of everything."

Spears, 26, and Federline, 30, tied the knot in a surprise backyard ceremony in Studio City, California, on Sept. 18, 2004. They are parents to Sean Preston, 3, and Jayden James, 2.

See more celebrity wedding photos.

In November 2006, Spears filed for divorce, citing irreconcilable differences. Their split was finalized in July 2008 after a contentious court battle. Federline won sole legal and physical custody of their children, but Spears has two visits and an overnight per week.

Remember these ugly Hollywood splits?

Spears - who is under a permanent conservatorship of her father, Jamie - reveals intimate details of her life the documentary.

See photos of Britney and her parents.

In a clip released Tuesday, the singer says her life can be worse than jail.

"Even when you go to jail, you know there's the time when you're gonna get out," she says. "But in this situation, it's never ending. It's just like [the movie] Groundhog Day every day."

Her next album, Circus, hits stores Dec. 2.

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