Nicole Richie says her entire life revolves around new baby Harlow – with one exception.

"Joel actually changes more diapers than I do," the new mom says of boyfriend Joel Madden, in an interview with Extra airing Thursday. "It's his time with her. He sings to her .... He laughs with her, plays with her. It's amazing."

Otherwise, Harlow, who was born in January, is at the center of the TV personality's life.

"Everything I do is for her," Richie, 26, tells Extra. "I was so excited from the minute I found out I was pregnant ... and it's been nothing but an amazing ride since."

Although Richie is the first in her circle of friends to have a baby, "I feel like my group of five to 10 friends, they really love her, like she's theirs ... My friends never go outside for smoke breaks anymore, they don't curse, they are definitely more demure. It's actually been really interesting."