"Aside from the giant belly, you wouldn't know [she's pregnant]," said the Carnival Row actor, 43, adding with a laugh, "She's a force of nature, obviously, as we all know, as everyone knows."
"But it's been really impressive," he praised Perry, 35. "There's no complaining. She's just all about it. It's pretty awe-inspiring to see the way she handles herself at this time. It's just business as usual."
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
Dave M. Benett/VF17/WireImage Katy Perry (L) and Orlando Bloom in 2017
The "Daisies" singer said last week on Mix 104.1's Karson & Kennedy that she is "as excited as [she] can be" about becoming a mom for the first time, but admits to feeling "every emotion under the sun" during her pregnancy.
"I've been overwhelmed, I've been anxious, I've been happy, I've been overjoyed, I've been depressed," said Perry. "I've been all of it. The world is just a wild time, and it's a wild time to bring life into the world."
"People were already having those kinds of conversations years ago where it was like, 'Man, the world feels a little uncertain,' and now it really feels shaky boots," she added.
Perry, whose new album is out Aug. 14, also said "there are a lot of rules" going into parenthood, and that "you start sacrificing" immediately. "You start becoming a mother, or a parent, once you conceive. Definitely," said the star.
Phillip Faraone/Getty Images Katy Perry and Orlando Bloom
RELATED VIDEO: Katy Perry "Is Still Decorating the Nursery" as She and Orlando Bloom Count Down to Baby
Katy Perry 'Is Still Decorating the Nursery' as She and Orlando Bloom Count Down to Baby
A source tells PEOPLE that Perry and Bloom have just "several more weeks" to go until the arrival of their baby girl
Perry also said she and Bloom "have yet to decide specifically on her name" for their daughter on the way — but they've "got options," and believe "she'll tell us" when she arrives.
"I'll look at her and go, 'Oh yeah yeah, you are her, you are that,' " explained the American Idol judge.
"He's really excited for a little girl," Perry said of her fiancé. "They say that little girls are 'Daddy's little girl,' that's how it's gonna be, [so] we'll see!"