Kevin Federline has Britney Spears on edge about what he might say in his upcoming book! As you likely heard, the former professional dancer is releasing a tell-all memoir called You Thought You Knew later this month. It comes nearly two years after the singer dropped The Woman In Me, where she spilled tea about their relationship. Now K-Fed is sharing his side of the story! And it has Brit "nervous as hell!" That's what a new report claims! Contents [hide] 1 Surprise! 2 MAD?? 3 Another Ex's Take 4 Other Looming Family Issues Surprise! According to a source spilling to Dailymail.com on Friday, the pop star was "blindsided" by the news of Kevin's book. Jeez. She didn't receive a warning that he was writing one? He didn't tell her in advance what he plans to say? Hey, Britney opened up about the romance in her memoir, so all's fair, right? Well, she reportedly felt like she held back a lot due to her fragile relationship with her kids at the time. Whether Kevin plans to give her the same courtesy? She doesn't know - and that reportedly makes her "deeply concerned," especially if his words will result in her getting ripped apart online. A business associate explained: "She is deeply concerned about this book. She feels that she held back on much in her book and worries how she will come across, especially as a mother." It's no secret that Britney struggled a lot personally - and Kevin witnessed some of those hard moments. Who knows what he'll divulge! The source continued: "The birth of her two children and then their split caused the most fragile times in her life along with the terrifying post-partum depressions. At times she felt that Kevin was against her being released from her conservatorship too." The insider explained there were "huge tensions" between Britney and Kevin over the years. For her part, the Toxic artist felt "abandoned" by her ex-husband following the birth of Sean and Jayden. How heartbreaking. He ended up getting sole custody of the kids, and she shelled out tons of money in child support payments to him for nearly two decades. Sadly, she was estranged from the boys for a while. Friends say their separation caused the "greatest pain and stress" of her life. Oof. Britney truly loves her sons. No wonder she feels so vulnerable right now! Related: Britney Spears' Exes Fighting! Kevin Federline Strikes Back After Sam Asghari Shade! Ultimately, she doesn't want to relive any dark period of her life again. It was hard to do so while working on her book, and the concern now is how Kevin's book could trigger her: "Her vulnerable state back then is not something she wants to relive in his book. She felt under her father Jamie's control. Her mental health issues were held against her for years - and used to control and manipulate her. All these times in her life are triggering. When she did her own memoir it was a deeply troubling experience. Who knows what this could do." Hopefully, Britney has a good support system around her... Though it doesn't sound like it, does it?? MAD?? What can she do? There's always mutually assured destruction, as they said in the Cold War. The business associate added that the Grammy winner still "has a lot to say about Kevin," but she bit her tongue for the sake of their children: "She knows how much her sons look up to their dad and have been centred in his world, and worries about impacting on that relationship. In truth, I feel that she held back in her memoir from spilling her whole truth because she was worried it would cut her off from the boys forever - and that they may never forgive her. It is a precarious situation. They are still working towards having a relationship with their mum and [becoming] high-profile teens. All these matters are very, very delicate to them." Will Kevin's book impact their relationship with him if he crosses a line with Britney? Will it cause her to say MORE?? Hmm. Maybe not. Maybe she'll keep the peace at all costs. The insider continued: "People can say what they want about Britney, but the one thing at her core is that she holds being a mother as her greatest achievement. She might not have the relationship with the boys she dreamed of, but her heart is all about those kids." That is one thing we'll never doubt about Brit! Another Ex's Take A former boyfriend of Britney, who asked to remain anonymous, also offered his two cents about the whole thing! He expressed "doubt" that Kevin ever "loved" the Womanizer hitmaker all! Whoa! Could you imagine if that bombshell were dropped in the book? Talk about a knife to the heart! The boyfriend mused: "It is complicated in so many ways. First I think Kevin walked out on their marriage and then used the California legal system to effectively fund his life [while] raising the two boys. He has been paid millions of dollars from her earnings. I doubt he ever loved her seriously. And in many ways he was the rebound after Britney and Justin Timberlake broke up and she was emotionally vulnerable f