CHICAGO (AP) – Three years after admitting he had sex with members of his staff, David Letterman says his marriage to Regina Lasko has never been better. Letterman tells Oprah Winfrey that he also feels better about himself. He says he’s trying to be the person he always thought he was “and probably was pretending” to be. He says he’s trying to find out why he did what he did. The interview airs Sunday on OWN.