Gwen Stefani and Gavin Rossdale Gushed Over Each Other Days Before Her 'Life Blew Up' Over Alleged Affair

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Hindsight is always 20/20, isn't it?

Amid a publicity tour promoting the current season of The Voice and her upcoming solo album, Gwen Stefani has been remarkably open while discussing her divorce from Gavin Rossdale. The couple called it quits in August of this year, just one month before they would have celebrated their 13th wedding anniversary.

"My life blew up in my face," Stefani said in an interview on Ryan Seacrest's radio show on Nov. 3. The 46-year-old singer went on to cite a "major event" that occurred on "the day after the GRAMMYs" that inspired her new single, "Used to Love You."

WATCH: Gwen Stefani Sheds Light on the Final Years Leading Up to Gavin Rossdale Divorce 

Now, a source tells ET that Rossdale had allegedly been engaging in a three-year affair with the family's nanny, Mindy Mann. As first reported byUs Weekly, Stefani is said to have learned of the alleged relationship after discovering explicit text messages, reportedly including nude photos and plans to meet up for sex, between Mann and Rossdale on the family's iPad. Reps for Stefani and Rossdale could not be reached for comment.

In happier times, just a few short months before the "major event" referenced by Stefani, the No Doubt frontwoman posted this sweet snapshot of she and her hubby on a family vacation in December. It is the last photo of the couple together on her Instagram account.

WATCH: 11 Times Gwen Stefani and Gavin Rossdale Got Real About Their Marriage and Kids

Cut to the GRAMMYs on Feb. 8: It was a big night for Stefani, who walked the carpet solo while Rossdale was on tour with his band, Bush. She hit the stage to perform alongside her Voice co-star, Adam Levine, and posted several shots to her social accounts on the day of the event.

WATCH: Adam Levine Defends His Bromance With Blake Shelton: 'He's All Mine' - Sorry, Gwen! 

Then, contrary to her usual frequent and cheery updates, Stefani's Twitter account went radio silent for nearly two weeks.

Stefani returned to social media on Feb. 20 to promote her cover story in Cosmopolitan Magazine, which had already hit newsstands on Feb. 10.

In Stefani's interview -- which would have been conducted weeks, possibly months, before the issue was published -- she confessed that her relationship with Rossdale wasn't perfect, but that they were able to make it work.

"We go through so much together -- it's a miracle that we could stay together this long," she told the mag. "[Gavin's] on a short tour right now, and he wrote me the sweetest note this morning. It's good to have those days when we both do our own things. I think that's what keeps relationships going, when both people can be themselves and have their own individuality. That's especially important for women -- it's hard to find time for yourself."

She also couldn't help but gush about her husband's good looks.

"I never really saw myself landing a guy that hot. I don't know if I was a nerd in high school, but I definitely wasn't the super-cute cheerleader so I never saw myself getting somebody like that," she said. "But I do think he's quite handsome. It's not the most important thing about him, but it is nice...and he makes really cute babies!" 

WATCH: Blake Shelton Gushes About 'Awesome Night' With Gwen Stefani in Nashville 

In an interview with the TODAY show in January, Stefani was literally brought to tears while discussing her relationship.

"If I look back on the whole thing, the one thing that's been constant is that we both want the same thing," she said. "We both want to be married. We both want to be good parents, and I feel really proud of what we've done together and that we don't -- you're gonna get me crying, no don't, I'm going to get all emotional! But I am really proud of it."

Rossdale echoed her sentiments in separate interviews with Rolling Stone and TODAY around the same time.

"She's taught me how to be a better person," he told Rolling Stone in January. One month later, in a live interview on Feb. 26, Rossdale told TODAY's Matt Lauer, "I think she sets the bar so high for any kind of measure of success in our household, that you've got to really come in firing on all cylinders and I'm not sure I can do that."

WATCH: What You Didn't See on TV From Blake and Gwen's First 'The Voice' Show as a Couple

Mann has been spotted out and about with the Stefani-Rossdale family since 2012, when images surfaced of Rossdale placing his hand on her backside during a hike with his children. Mann was last seen on a family outing in February of this year.

Now, Stefani has moved on with fellow Voice coach Blake Shelton, who is also newly divorced. Reps for the pair confirmed their relationship earlier this month.

A source told ET on Wednesday that Rossdale is "bummed that the marriage is ending, but he wants Gwen to be happy. If being with Blake makes her happy, so be it."

For more on how Rossdale is handling Stefani's new romance, see the video below.