Kelly Clarkson is opening up about her "embarrassing," tear-soaked performance of "Piece by Piece" on American Idol last week - and pointing fingers at 20-month-old daughter River Rose .<br />"I didn't realize it was gonna be that bad," Clarkson tells Ellen DeGeneres on Thursday's episode of Ellen .<br />Clarkson, the original American Idol winner, sang during her stint as a guest judge on the series' final season.<br />The 33-year-old says part of her emotional response was due to the nostalgia factor: "My 1-year-old is running around the same hallway as I was [at] 19."<br />Clarkson's pregnancy with her and "great husband" and "great father" Brandon Blackstock 's second child - a son - also played a role.<br />"River is constantly watching Finding Nemo ," says Clarkson, adding to the host, "I feel like we live together, you're always in my house."
