Despite telling PEOPLE in August that he never saw himself "sitting down and writing songs" with his now-girlfriend Gwen Stefani, Shelton, 39, confesses that he was just a bit hesitant at the time to publicly talk about any potential collaborations.
But as the "Used to Love You" singer revealed on Twitter, the couple's duet "Go Ahead and Break My Heart" will be featured on Shelton's upcoming album If I'm Honest (out May 20).
"We were at a point where it's like, 'Do we want to go there? What will people think?' And then we finally just got to the point where it's like, 'You know what? I don't give a s---," the country star told PEOPLE exclusively at a Voice event (benefitting Children's Hospital Los Angeles) Thursday about the song the duo co-wrote at the end of October.
"I love this song! This song's important to us and the fact that we wrote it together is so important to both of us," added Shelton.
"Look what I found lying round the house! #ispymyname #goaheadandbreakmyheart @blakeshelton #eeeekkkk! #crazy!" Stefani wrote on Twitter Tuesday.
Look what I found lying round the house! :face_with_rolling_eyes:#ispymyname #goahead andbreakmyheart:broken_heart: @blakeshelton #eeeekkkk! #crazy!:stuck_out_ton gue_closed_eyes: Gx pic.twitter.com/ZI0Kz4Ve9j‹ Gwen Stefani (@gwenstefani) April 19, 2016
On the songwriting process with his girlfriend, Shelton admits, "I'm insecure about my writing and who I write with and I don't know – I'm just weird about it sometimes."
And despite coming from two different musical worlds, the couple felt an instant easiness together in the studio that made writing and recording "Go Ahead and Break My Heart" extra special.
"I think Gwen has a smaller circle too when it comes to writing, and the fact that we went there that early as we were getting to know each other, it's just remarkable," said Shelton. "As different as we are musically, we're a fan of the same type of songs. We have these playlists that we send each other that are stuff that we loved growing up and they're so similar, so I think it made it easy for us to collaborate."
Shelton also gushed about Stefani, calling her "the coolest girl in the world," although he did divulge that he was quite nervous to be singing with the Gwen Stefani.
"I'm intimidated by Gwen all the time," he joked. "Any time I take a step back and think, 'Wow, to me she's Gwen, but she's Gwen Stefani, you know what I mean? It's like a self check every now and then. Whoa, I'm hanging out with literally the coolest girl in the world and I get to hang out with her. Just having a meal with her sometimes, it's like, 'Whoa, that's her sitting up there!"