Kelly Clarkson and Brandon Blackstock (inset)
Kevin Winter/Getty; Inset: Courtesy Brandon Blackstock
is known for empowering breakup songs like "Since U Been Gone," but now that she's happily in a relationship, the pop star is struggling to find her edge.
"It is killing me," Clarkson told PEOPLE while doing press for ABC's upcoming singing competition show Duets
. "I'm trying to write a tough song and it is coming out like butterflies and rainbows."
, 30, says she has been dating Nashville-based talent manager Brandon Blackstock, 35, since late 2011.
"It is ruining my creativity," she joked of the relationship that she publicly announced in early March. "I'm writing all this happy [stuff]."
Blackstock is the son of Narvel Blackstock, Clarkson's manager of five years, and the stepson of Clarkson's "Because of You" duet partner Reba McEntire.
"People used to ask, 'Why are you single?' and I'd say, 'It is not in my schedule,' " Clarkson told reporters. "I'm in a relationship right now and I have time for it. I never used to."
Clarkson's next single off her fifth album, Stronger
, will be "Darkside" but her happy love life is making it difficult to tap in to her own darkness.
"People are going to be, like, 'What the hell happened to you,' " she said of her recent writing sessions. "It has been really difficult. I love it. It's an awesome problem to have."