LeAnn Rimes debuted her new single, "Borrowed," on "The Tonight Show With Jay Leno," last night (Dec. 18). The songstress admitted to the show's host that the tune, and her upcoming album Spitfire, tackle the subject of her affair with now-husband Eddie Cibrian.

"I actually still get embarrassed talking about it, even though I've written a whole album about the situation," LeAnn explained to Jay Leno. "I did go through a very public affair with Eddie, who's now my wonderful husband. People who haven't been in that situation, I guess, look into the darker moments of things. I think a lot of people think it's done with complete abandonment and it wasn't. I call myself pathetic in the song and I loved that word because it was the only way I knew how to describe myself, because I was pretty pathetic."

While the 30-year-old is open about the song's origin now, she was nervous to write it, for fear of what people would think. "I actually carried that lyric, 'I know you're not mine, only borrowed,' around with me for about eight months," she revealed. "I was afraid that if I wrote it, I would have to write it so honestly that I would offend, more so than I already had, everyone. I knew also that there's a lot of humanity in the truth that this is how I felt, because a lot people, I think, wanted to put words in [my] mouth [as to] how I felt. This is the truth, this is how I felt, and there's no beauty in it."

Despite being borne of a specific situation, LeAnn believes the tune has a universal theme. "This song, the chorus says, 'I don't want to give you back,'" she explains. "A lot of people who haven't been in this situation can relate because there's got to be a relationship in their lives -- romantic or not -- that it just kills to give it up. It's a very intimate look into a very rough moment in my life."

Since LeAnn is sharing such personal emotions with her new music, and her home life has been touched on in Bravo's "The Real Housewives of Beverly Hills" -- Eddie's ex-wife, Brandi Glanville, appears on the show -- Jay asked if it felt weird having such info available to the public.

"There's no reality in a reality show," she answered. "I guess it's not weird when I know that's not my reality. Here's the therapy coming out in me; the positive, I should feel flattered that I'm that interesting. That I can be such an amazing storyline on a reality show. [laughs]"

Spitfire is due out in spring 2013.

Watch LeAnn on 'Leno'