"I'm feeling really good, and just the outpouring of love and support has been really amazing," the 41-year-old actress told Access Daily's Mario Lopez. "There's been a big 'ol mom tribe that comes up. I've heard about it, but they really come up in full force."
"There's a really great dad tribe, too," she added. "Everyone who comes up is really supportive, and it means so much to me."
As for whether the couple will learn their baby's sex ahead of his or her birth, it doesn't sound likely.
"I haven't decided if I'll find out yet or not," she said, adding, "It's a good surprise to find out. There's very few surprises in life."
Ironically, Munn's pregnancy was one of those surprises, even though there had been speculation swirling for weeks.
Her boyfriend, 39-year-old comedian John Mulaney, confirmed the news on Tuesday with a very specific and arguably suspicious timeline of events.
It raised a few eyebrows.
"I went to rehab in September, I got out in October, I moved out of my home from my ex-wife, [Anna Marie Tendler]," he explained on Late Night with Seth Meyers.
In December, he said he "went to rehab again, this time for two months. I got out in February, I lived in sober living for another month and a half. ... Then in the spring, I went to Los Angeles and met and started to date a beautiful woman named Olivia."
"I got into this relationship that's been really beautiful with someone incredible," he added. "And we're having a baby together. I was nervous when I was about to say the news!"
In between his rehab stints, John got a job working as a writer for Seth's show. He thanked the late-night host for his involvement with intervening on him, also noting to the audience that he first met Olivia at Myers' 2013 wedding.
Following Mulaney's proclamation, a celebrity agent who claims to have worked with Munn in the past told Page Six they were suspicious of both the series of events and the way in which the comedian presented them.
"I don't think it's any coincidence that John broke the news of Olivia's pregnancy the way he did in terms of basically giving a timeline of his past few months – when he moved out of his house, how it was the spring when he fell in love with Olivia," the agent said. "It seems to me that he is going to great lengths to dispute the idea that he cheated."
Prior to John – who's a former Saturday Night Live writer and has hosted the program several times – Olivia dated other high-profile men, including SNL alum Will Forte.
"She has a demonstrated history of hanging out with and spending time with 'SNL' guys, so no way did their paths not cross, and there is the video of them together back in 2017," the agent said.
Indeed, John and Olivia were seen on camera together for Jon Stewart's special, Night of Too Many Stars, during which Munn was heard saying, "Hi, John!" as Mulaney walked past her off stage.
In May, it was reported that the comedian and his estranged wife, Anna Marie Tendler, had called it quits; he officially filed for divorce in July.
Also in May, it was reported that he was dating the actress, who had previously considered herself an "obsessed" fan.
Interestingly, sources close with Tendler told Page Six that Mulaney had actually asked her for a divorce after his second rehab stint in February and not after he left treatment in the fall of 2020, like he had said on Meyers' show.
In May, a Mulaney source told People that his relationship with Munn was "very new" and that the two "met at church in Los Angeles."
One insider told Page Six that claim "was BS, and Twitter immediately called Olivia out on it, saying she's known John for years."
"It isn't entirely clear when their relationship started," added the insider. "There have been rumors for months about her being pregnant, and it all just seems like a very tight timeline."