The actress and model, who has been engaged three times and recently split from ex-Gladiator David McIntosh, told The Mirror that she thinks she is "too judgmental" with men.
"The older you get the more you realise you know nothing about relationships," Kelly said. "I have no idea. I don't know anything. I had much more successful relationships when I was in my 20's and I knew nothing.
"But now I feel like I can work people out so quickly and it's not good. Being judgmental is not good."
Kelly added that she is "completely single at the moment" and is enjoying living in LA with her fellow British actress friend Natalie Loren.
"There's no boys messing up the house. I'm like, 'Are you going on a date tonight?' And she's like, 'Nah let's watch a movie.' It's a no-boy zone."
Kelly is currently living in LA while working on her new sitcom One Big Happy, which is produced by Ellen DeGeneres and sees Kelly playing a British girl called Prudence.
In the show Prudence marries Luke (Nick Zano) after a whirlwind romance, only to discover that he is having a baby with his lesbian best friend Lizzy (Elisha Cuthbert).
Kelly laughed that she has something in common with her character, explaining: "Some of the relationship choices I make are on a whim!"
Kelly's ex David recently revealed that he is planning on writing his autobiography.