Cowell met Hussainy in 2003 when she worked as a makeup artist for "American Idol." They began dating in 2009 and got engaged in February 2010.
"It's quite a complicated relationship. We have had a break from each other and we are still incredibly close.
I'm vulnerable. It's not on, it's not off, it's somewhere in the middle. I don't know if I will ever get married, but I am happy," Cowell told the Sunday Mirror in London.
He also said he got carried away when he described Hussainy as "the one" during an interview on "Piers Morgan's Life Stories."
"I have been pretty good about not talking about my private stuff but I got caught up in the moment," Cowell said.