Jason Trawick Mocks Fiancee Britney Spears!

Jason Trawick and Britney Spears on May 11, 2011 in Beverly Hills, California. Credit: David Livingston/Getty Images

He won't be a slave for her!

Britney Spears' constant demands that fiance Jason Trawick "check in with her" have him fuming, a source tells Us Weekly.

"The romance is gone," says the insider. Trawick, 40, "puts her on speakerphone so friends can hear her nagging."

(A rep for the X Factor star, 30, denies this, and an insider insists, "That's not Jason's style. They're happy.")

But the source contends there's turbulence ahead: "I'd be shocked if they got married."

Spears, who is a mom to Sean Preston, 7, and Jayden James, 6, (with ex-husband Kevin Federline) got engaged to Trawick in December 2011, but have yet to set a date.