Christina Perri wants to be honest about motherhood. The 38-year-old singer – who has Carmella, six, and Pixie Rose, 22 months with husband Paul Costabile – has turned her hit song ‘A Thousand Years’ into a book about being a parent and wanted to showcase her “real life” with the project and be open about things like lack of sleep. She told People: “All I do is live my real life, in the season of motherhood and singing to my girls. It’s been my favourite part. It made so much sense. With each of these projects, we didn’t overthink it or try something that was inauthentic. I didn’t want to go b…