The notoriously private actress covers Elle's September issue, in which she talks about hitting the milestone age of 30 this year, and also reveals her baby girl's name for the first time -- Edie! Keira welcomed her first child with her husband, musician James Righton, in May.
"The love thing is astonishing. It's a very primal, primal love. That's quite extraordinary," she says about her relationship with her child. "And the ability to have no sleep and continue going. It's not pleasant -- I never thought that I could actually do it for the amount of time that I've done it."
Keira shares that giving birth has also actually made her much more accepting of her body than ever before.
"I have to say, as a woman, you hate certain parts of your body. You go through those periods where you look in the mirror and you think, 'Oh, if only I had different legs or arms or whatever,'" she admits. "[But then] you go through pregnancy and labor and then feeding the kid and you go, 'Wow, my body is totally amazing,' and I'm never going to not like it again, because it did this, and this is f**king extraordinary."
Keira, who turned 30 in March, says that she's happy to get past her twenties, surprisingly calling the time "pretty crap."
"As a person, you’re changing so much and you’re trying to figure stuff out. Some people go wild and have a great time and throw caution to the wind, and I was the complete opposite," she explains. "I was very shy. It took me a lot of years to try and stop pleasing a lot of people and allow myself to have fun. It's the difficult thing of getting out of your own head. To stop going, 'Oh, there's something I should be doing, there's a way I should be behaving, I should be dressing….' All of those shoulds, you can drown in them."
She is now completely open about having seen a therapist at the time.
"I highly recommend it," she stresses. "I don't do it at the moment. But in my early twenties when I found everything completely overwhelming, 100 percent, I did it! Are you kidding? I think when you're in those moments in your life, and you want to get through them…you have to do whatever it is to help you get over it. You have to give it a go. Try anything that might help."
In January, ET caught up with the British actress at the Golden Globes, when she hilariously confessed that going to the annual awards show pregnant was a "very sober" experience. "I'll remember everything tomorrow," she laughed. Watch below: