Since Jessica Simpson and her fiancé Eric Johnson welcomed their daughter Maxwell Drew on May 1, "life has completely changed," Simpson, 31, tells PEOPLE exclusively. "From how I sleep to what I think about, Maxwell has definitely taken over everything!"
In this week's issue, Simpson and Johnson give an exclusive interview, plus share the first photos of their little one, who's inherited her mom's eyes and her dad's calm demeanor.
"We stare at her all the time," says Simpson. "We can't get enough!"
But becoming new parents hasn't been without its hardships. Recovering from surgery – Simpson delivered via C-section – isn't easy, she says, and nursing, which she does throughout the day, has become "a full-on job."
Still, "It's the worst if I have to pump and give Eric a bottle to give her," says Simpson. "I miss holding her and having that closeness."
For more exclusive details about Maxwell's first few weeks at home – including all the details of her birth, Simpson's plans for a wedding and more children, and first photos of the new family – pick up this week's issue of PEOPLE, on newsstands Friday