ET caught up with Katherine backstage after her appearance on The Late Late Show to talk about her family, plans for the future and new TV show Doubt.

Katherine Heigl & Joshua Bishop Kelley Jr.

"I think once you have two, it doesn’t matter anymore!" laughed the Doubt star, while pondering whether three kids are exponentially harder to handle than two. "You’ve already got two…right!?"

Asked if she was hinting that she wants to further expand her brood, Katherine admitted that she’s already raised the subject with her musician husband, Josh Kelley.

"I’ve already tried to have this conversation, but it’s so funny – at eight weeks, he’s like, ‘I’m not talking about this right now!’" she said.

Katherine also said that she had been trying not to put herself under any pressure post pregnancy. "I didn’t emotionally, mentally or physically go, ‘I’m going to beat my body into submission,’" she shared. "I just went, ‘You know what? Just relax about this.’ Sometimes the more focus I put on dieting and getting in shape, the harder it is for me to do it. I don’t know if I become more food-obsessed or what happens, but this time around I just said, ‘I’m going to give myself whatever time I need. I don’t want to kill myself over this right now.’"

In Doubt, Katherine describes her character Sadie Ellis as "ambitious and she’s smart and she’s talented, but she has these flaws and vulnerabilities and this baggage" – but admits that’s she’s struggled a bit with the legal jargon, moreso than the medical terminology she used to memorize for Grey’s Anatomy.

"I don’t know why, for some reason I’m stumbling up on the legalese more than I did with the medical jargon," Heigl said with a laugh.

Catch the Doubt premiere tonight, Wednesday 15th on CBS at10/9C.