Weeks after Blake Shelton and Gwen Stefani finally confirmed they'll be releasing a duet together on the country star's upcoming album, fans of the couple will get to hear the song (now available on iTunes) when they perform it together Monday night on The Voice. 

"We're a little bit nervous about it, but nervous in a way that we can't wait and nervous in a way that we hope people think it's as good as we think it is," Shelton tells PEOPLE exclusively about debuting "Go Ahead and Break My Heart." "It's like people getting a look at something personal for the first time." 

Ahead of Monday's show, Stefani shared a selfie of Shelton kissing her forehead as the pair posed beside a tree carved with "B+G." 

Shelton and Stefani – who began dating last fall – co-wrote the song together "about some serious insecurities that we had when we first started down this road with each other," he says. "We both had trust issues. We were getting over it, but we wrote this song about it, and it's perfect." 

What makes the duet extra special is "the honest way it came about," adds Shelton, whose new album If I'm Honest is out May 20. "There's not a third ghost writer, there's not five writers on it. It's just she and I sat down and wrote this song … and I couldn't be happier about [it]." 

Both stars went through tough divorces last year (Shelton and Miranda Lambert divorced in July and Stefani and Gavin Rossdale announced their split several weeks later) and struck up a close friendship before their relationship turned romantic. 

"It was a really super unexpected gift to find a friend, somebody who happened to be going through the exact same thing as me, literally mirroring my experience," Stefani said earlier this year. "I don't think it's an accident that that happened. It saved me." 

The Voice airs Mondays and Tuesdays at 8 p.m. on NBC.