The couple confirmed their relationship in April this year after meeting at the premiere of Red Riding Hood, and announced their engagement only months later at the MTV Movie Awards.
"Well yeah, I'm not allowed to say too, too much about that stuff, but it's going good," McDonald coyly told MTV News, when asked about the couple's wedding plans. "I love her to death."
The singer admitted that he would never have predicted the two would get engaged so soon after meeting, but said that it had simply been love at first sight.
"It's kind of one of those things you don't expect," he explained. "Like last year I never would have thought I'd be getting married."
"She's the perfect girl," he added. "We fit each other, when you know, you know, and she's the one."
McDonald is currently starring alongside the likes of Casey Abrams, Lauren Alaina and winner Scotty McCreery on the American Idol US tour.
Watch Paul McDonald and Nikki Reed's first meeting at the Red Riding Hood premiere below: