The British actress and singer - who has always refused to name her son's father - is amazed at how much her life has changed since she gave birth to 13-month-old Henry, but is now used to putting him first.
She said: "If he's sleeping I'm trying to sleep and when you're breast feeding you're the milk machine.
"There's no time to pick up the guitar, much less go for a walk or have a beer. The first year of Henry's life has been just an insane earthquake for me."
The 39-year-old star - who is preparing to start work on a new album - says she always planned to be an older mom because her movie and music commitments were as fulfilling to her as raising a family.
She added: "I waited a long time to have children because I had this career that was kind of like my kid, it required as much nurturing.
"There's no amount of hassle that could be bigger than my love of Henry."
The 'Motherhood' star has sought advice on raising Henry from an internet support group, but admits her schedule is so hectic she scarcely has the time to use the resource properly.
She explained: "I use the site called 'Mamapedia' that's amazing, where you can ask questions and mothers across America can answer, so you can get maybe ten answers and it's kind of a cool resource. But sitting down and reading about somebody else's tough experiences of being a mother, you're suddenly like, 'My God, I've got a kid and I don't have time to read about this. I've got to go do it."