The reality TV star, who has the 13-month-old with partner Scott Disick, admitted that it "doesn't feel good" when she travels without him.
She told Parenting: "Unless I'm working, I can't be away from him without feeling guilty. It doesn't feel good or natural to be, so it's a struggle.
"I don't want to judge, but I've also met women who think it's cool to be out or away from their baby, and I don't get that. Every time I'm not working, he's with me.
"Even on an airplane, he is with me even if the nanny is also on the plane. Any time I can have with him, I am lucky to have."
Kardashian also said that she and Disick have become so accustomed to always being with Mason that they've stopped enjoying evenings out together.
The 31-year-old explained: "My friends keep saying, 'You and Scott should go out and eat or do something'.
"Recently my sister Kim watched Mason so we could go to dinner. It took so long - actually, it probably didn't take so long, but to us it felt like it took long - we were like, 'Should we just get pizza and go home?'
"Scott says he doesn't need to wine and dine me anymore. We would be just as happy having a slice of pizza sitting in bed with our son."
Kardashian insisted that when she does have time away from Mason, she is happiest leaving him with her stepfather Bruce Jenner.
She added: "Out of everyone, I call Bruce for help the most. He's a perfect role model for him. He takes Mason to the car wash for 'man time'."