In the book, Simpson explained she initially just wanted a partial tummy tuck, but it had nothing to do with weight loss -- as she weighed 107 pounds at the time. "I wanted to get rid of the stretch marks and loose skin left sagging from my back-to-back pregnancies," she explained, having just given birth to son Ace and daughter Maxwell.
"I was so ashamed of my body at this point that I wouldn't let Eric see me without a white T-shirt on," she explained. "I had sex with it on and even showered with it on. I couldn't bear to look at myself."
While she said she was "not strong enough" to be proud her body created life, she hopes readers will. "It touched on all my insecurities," she said, "and I couldn't handle it."
While on vacation, she got a call from her doctor, who said he could not approve the operation, even though the plastic surgeon did. "I'm looking at your liver levels. You could die," he told her. At the time, she was drinking heavily, as well as relying on both stimulants and Ambien.
"I was killing myself with all the drinking and pills," she said, adding that she and husband Eric Johnson were "in denial" about their alcohol intake after hearing the news. Instead of heeding the doctor's warning, they both got drunk, with Eric telling her -- in front of their friends -- that she "shouldn't be so selfish" to risk her life.
She kept ignoring her doctor's orders and got the partial tummy tuck, but still didn't love how she looked after. "I still had loose skin that hung over my pants," she wrote, adding that she got a full tummy tuck two months later.
"This surgery was more involved. There was a sense that something was going to go wrong from the get-go, even though I stopped drinking to prepare," she said. "It did not go well. I got an infection — colitis — and was vomiting so much I thought I was going to bust my sutures. My mom and Eric were so worried. They had to rush me to Cedars, and I secretly stayed there for nine days."
Simpson said the complications were hard on her husband, who loved her at any size and believed "he should have talked me out of going through with the surgery."
"I can tell you that plastic surgery does not cure what's inside," she added. "Really, it's about how you feel emotionally, and I was still just as hard on myself once those stitches were out. I still had work to do."
The singer has been sober since 2017. Her memoir, "Open Book," is available now.