Chrissy Teigen Was 'Shocked' by Pregnancy, Says Source: 'It Really Was the Happiest News'

John Legend previously called his third baby on the way with wife Chrissy Teigen "a little quarantine surprise"

Chrissy Teigen's third baby on the way couldn't have been a more joyful surprise.

In this week's issue of PEOPLE, out Friday, a source says the model, cookbook author and Chrissy's Court star, 34, "was pretty shocked when she found out that she is pregnant."

"It really was the happiest news, though," the insider adds. "She cried many happy tears and was very emotional."

Teigen and husband John Legend have been open about how they previously underwent in vitro fertilization to conceive their two children: son Miles Theodore, 2, and daughter Luna Simone, 4.

"It was a surprise. A little quarantine surprise, I guess you could say," Legend, 41, said Monday on the Today show of conceiving their little one on the way during the ongoing coronavirus (COVID-19) lockdown.

John Legend and Chrissy Teigen with daughter Luna and son Miles. Chrissy Teigen/Instagram

"But we're very excited, and we're grateful for all the well-wishes we've gotten from people all around the world," he added. "Thank you so much."

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Chrissy Teigen. Chrissy Teigen/instagram

Multiple sources confirmed Teigen's pregnancy to PEOPLE after she and Legend first hinted their family was growing in the music video for the Grammy winner's song "Wild," which was released on Thursday.

Two days after the happy news broke, Teigen set the record straight on the timing (as many fans had noted that she recently underwent breast-implant-removal surgery), revealing that the "routine pregnancy test you do before surgery" said negative, and she only got a positive when testing again weeks later.

"So we prayed to the boob surgery gods that everything would be okay. Went to every appointment terrified. Even without the surgery, I didn't think I could get pregnant naturally anyway. So the odds just felt ... bad," she added, in part. "But what they say so often can be true. When you give up on trying, life has a way of surprising you."

The soon-to-be mother of three went on to share that despite the good news, she's still "very worried," as their unexpected road to baby No. 3 is much different than how their first two children were conceived.

Chrissy Teigen and John Legend with daughter Luna and son Miles. Chrissy Teigen/Instagram

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"Part of me misses the safety of my perfect embryos, created in their little dish. They felt untouchable and safe," Teigen explained. "IVF was an amazing choice for us to be able to make. So hard, but we got two beautiful monsters out of it. I promise you, I never ever ever ever ever thought I could [get pregnant naturally]."

As for how her kids are taking the news, Teigen revealed that they're not on the same page. "Luna is very, very excited," the Lip Sync Battle host tweeted. "Miles, not so much. Jealous!"

The source tells PEOPLE in this week's issue that now that the initial shock and worry has settled, Legend and Teigen are "very happy" and keeping busy with Luna and Miles. "They take turns working and caring for the kids," says the insider. "They are a great team."

For more about Chrissy Teigen and John Legend's growing family, pick up the latest issue of PEOPLE, on newsstands Friday.