Blake Shelton's upcoming new album features a duet with his girlfriend, Gwen Stefani, but he admits they both had to overcome some nervousness to collaborate on the track.

Shelton is set to release If I'm Honest on May 20, and he's hinted that the album is the most personal that he's ever recorded and may provide some insight into his divorce from Miranda Lambert in 2015. He revealed the cover art on The Voice on Monday (April 18), and the following day Stefani revealed the track listing via Twitter, including a song they perform together titled "Go Ahead and Break My Heart."

They co-wrote the song in October of 2015, before they'd even confirmed their relationship in public, and they were initially hesitant. "We were at a point where it's like, 'Do we want to go there? What will people think?'" Shelton tells People. "And then we finally just got to the point where it's like, 'You know what? I don't give a s--t.'"

It wasn't just other people's perception that they were worried about, he says.

"I'm insecure about my writing and who I write with and I don't know — I'm just weird about it sometimes," Shelton admits, adding, "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."

Singing the song with Stefani in the studio might also tend to bring out some self-doubt.

"I'm intimidated by Gwen all the time," he jokes. "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!'"

Fortunately, despite performing in very different genres, the couple actually have a lot of musical influences in common, which helped make their collaboration easy. The results were worth any obstacles they had to overcome, Shelton says. "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."

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