Britney taunts K-Fed with her sexcapades!

While she is having a ball with music producer J.R. Rotem, pop singer Britney Spears is also not missing any opportunity of taunting estranged husband Kevin Federline about her latest fling.

Sources say that Britney recently called Kevin to ask him if he'd seen pictures of her kissing Rotem and then bragged about a sexual escapade she'd just had.

And as if this wasn't enough, she added salt to his injury by taunting him about the lavish lifestyle he is missing out on since the split.

"It was really bad," TMZ.com quoted an eyewitness, as telling In Touch Weekly.

"[Brit] just started pushing his buttons ... he started screaming at her," the eyewitness added.

Meanwhile, Kevin is reportedly gathering evidence of Britney's wild partying to use against her in a custody battle over their sons.

Spears might have cheated on Federline

Pop superstar Britney Spears might have cheated on her now estranged husband Kevin Federline before they split.

Spears is now dating J.R. Rotem, a friend of Federline who produced many songs on Federline's latest album. He is now working on Spears' comeback album. But sources say that Spears and Rotem were involved even before she filed for divorce, reports newsweek.com.

Another source adds that there was "definite chemistry" and Spears waited till she filed the papers. There are also rumours that Paris Hilton dated Rotem.

Rotem worked on Hilton's album and they dated for a while.

A source says: "It was nothing serious, just a few hookups. I bet a million dollars that Rotem tried to keep that a secret from Britney. Britney would probably flip out if she knew that he'd romanced Paris first."

'My name is Kevin Federline, not K-Fed'!

Pop diva Britney Spears’ estranged husband Kevin Federline is once again in the headlines, but this time for saying he hates his nickname K-Fed, and his warning to wrestling star John Cena.

Federline, who is to take on the World Wrestling Entertainment (WWE) star on the New Year’s Eve, has said that he hates his nickname K-Fed.

He is also hopeful of overpowering Cena when he faces the 240-pound wrestler in Miami, Florida, at the end of this month.

"The real Kevin Federline never backs down from a challenge. Make all your jokes, because New Year's Day I'm the one who is going to be laughing," Contactmusic quoted him as saying.

"Oh yeah, Cena, my name is not K-Fed, it's Kevin Federline, bitch, and I want some and I'm gonna get some," he added.

Federline had entered into a contract with the WWE earlier this year for participating in "staged" fights with professional wrestlers.