Britney Spears Says She Loves 'Sex,' Rehearses for Vegas in E! Doc Preview (Video)

Britney Spears is opening up in E! documentary I Am Britney Jean.

The two-hour special airs Dec. 22 at 9 p.m., five days before the 32-year-old pop singer unveils her two-year residency, Britney: Piece of Me, at Las Vegas' Planet Hollywood. I Am Britney Jean will offer "an intimate look at one of the most overexposed yet under-revealed stars of today as she faces one of her biggest challenges ever while finishing her album, shooting videos, doing press -- and being a mom," according to E!.

In clips released Thursday morning, Spears, a mother of two young boys, is seen discussing sex and how her perspective on it has changed over the years.

PHOTOS: Britney Spears: A Look Back at the Pop Princess' Best Costumes

"I love sex. I think sex is great, but I feel a little different about it not that I'm older," she admits. "Sometimes I feel like I'm 20, and then sometimes I feel like I'm 50."

In another clip, Spears is seen working out new choreography to one of her old hits, "Toxic," with co-choreographer Antony Ginandjar 112 days before the Las Vegas show opens.

"This year I have new choreographers. They're new, up-and-coming, fresh guys, so their stuff is really hard," Spears says, adding that it's "rewarding" to do something that's difficult.

Twitter: @insidethetube