"Katie and Jamie have been dating for a while," an insider reveals to In Touch, adding that Jamie has secretly been spending time at Katie's apartment. "They're very Mission: Impossible about their romance."

A second source confirms to In Touch that one early morning in mid-September, a driver pulled in front of the Trump Soho Hotel, prepared to take Jamie to the set of his new flick Annie -- but was surprised when Katie stepped into the limo instead. "A hotel employee confirmed that Katie had stayed at the hotel with Jamie and that she was taking his car," the second source reveals. "So the driver drove her home to her Chelsea apartment."