A source told Us Weekly: "She goes from performing high-intensity shows to being the mom of three very active boys. It finally caught up with her."

On February 5, the blonde beauty revealed she felt "under the weather" - which meant she wasn't able to take to the stage at Planet Hollywood.

At the time, Gwen insisted she would be doing all she could to return in time for her gigs on February 8, 12 and 14 - but she ultimately had to cancel those dates, too.

Meanwhile, Blake Shelton - Gwen's boyfriend - recently confessed he wants to forget what he was like before he started dating the pop star.

The 43-year-old singer - who started dating Gwen in 2015 - reflected on his romance with his partner, saying she's made him a much nicer person.

Speaking to 'The Voice' co-star Kelly Clarkson, Blake said: "I don't want to remember what I was like before Gwen, actually.

"I'm a little bit of a jerk to you still. But I was a jerk to everybody ... Look how nice I am now!"

Gwen also got emotional as she revealed how much her own life has changed thanks to their relationship.

She added: "Blake saved my life, everybody knows that.

"Like, we're just having the time of our lives, and we never expected that this late in our lives, so we're just trying to savour every moment together, and just to be back on 'The Voice' as well - not to change the subject - but working together again has been really fun, and I love being here and I love being with him."