"He's six weeks and getting fat. It's very exciting. All that time on the boob is starting to result in growth," the Homeland star, 33, told Giuliana Rancic on E!'s Live from the Red Carpet at the SAG Awards.
"He's getting rolls ... thank goodness they've arrived. He's starting to smile a little bit and he kind of knows I exist," she added. "That's reassuring – that feedback is amazing."
Winner of best actor in a TV series – drama for her role as Carrie Mathison, a Central Intelligence Agency officer, the new mom said her marriage to Hugh Dancy helps her step out of character once filming is done.
"I'm able to disassociate," the actress, wearing a one-shouldered Givenchy dress, said. "There are all these unconscious rituals that help me engage and disengage – like taking my wedding ring on and off helps free me up. I wouldn't be able to sustain it otherwise."