The singer and actress, who has spoken publicly before about eating disorders, revealed that she got back in touch with an old psychiatrist to talk over how she was feeling about her changing body.
WATCH: Katharine McPhee films inside beautiful home with David Foster
Katharine was pregnant throughout most of 2020 and welcomed her son with husband David Foster in March 2021.
"Even though you know your body is going to change, and you expect that, if you're someone who has control issues with your body, psychologically, it just does something different," she shared on Katherine Schwarzenegger Pratt's Instagram Live series.
"It played with my mind a little bit. I was losing control and I was going back to this old disordered version of myself, which was upsetting because I just wanted to enjoy my baby."
Katharine, 37, then revealed that her psychiatrist helped her to "overcome disordered behavior" by "not obsessing and letting my body tell me what was needed, not being like, 'It has to be oatmeal in the morning, four ounces of protein,' because that makes me crazy."
Katharine and David welcomed their first child together
When podcast host Katherine asked if she had advice for self-love, the former Smash star said there is no "secret recipe for it".
"For me, I had to take the steps, walk through it, to kind of find self-love. I think it's reasonable to say that you don't always have moments of self-love," she shared.
"I really struggled during that first trimester. It was difficult for me to find that self-love, self-appreciation. But then I found it later. I think how I found it is something that I'll now carry with me.
"I really feel like having conversations with yourself are important, because I'll often find myself talking through a situation, like you'd have with a girlfriend, but to yourself."
Katharine looked sensational in a red swimsuit as she defended husband David's comments
In December Katharine came to husband David's defense after the 72-year-old was slammed by negative criticism for jokingly asking "what baby?" when sharing a picture of his wife in a bikini.
"I lost this baby weight without dieting. Zero. Diets are the worst and I've had zero pressure from anyone. I've let my body do its thing and found a great workout. That's it," Katharine hit back.
Friends and fans rushed to comfort the actress, with Debra Messing commenting: "Brava! And send me your workout."
Rachel Zoe remarked: "You get them, lady, you look [fire emojis] and I love that David Foster is crushing on his wife. Haters gonna hate."
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