Article continues below advertisementWas Britney Spears the "Womanizer" herself?The pop star's ex-husband Kevin Federline shockingly accused Spears of cheating on him with a female backup dancer while they were dating more in his upcoming memoir You Thought You Knew - which hits bookshelves on Tuesday, October 21.An excerpt of the tell-all memoir exposed a night Spears and Federline went out in Amsterdam in 2004.Article continues below advertisementSource: MEGAKevin Federline claimed Britney Spears 'made out' with her backup dancer Teresa Espinosa while they were dating.