While Kim - who's carrying her second child - says she "hates" being pregnant, Billie absolutely loved it.
Mum to 16-month-old daughter Nelly, the pretty reality star said: "I feel sorry for Kim Kardashian, there's nothing worse than not feeling 100 percent happy, confident and comfortable when you're pregnant.
"It must be really horrible. I loved being pregnant and had a really great experience, so I don't know what it feels like."
Billie – who is hoping to expand her family with fiancé Greg Shepherd next year – adds: "I've had friends who've had difficult pregnancies, they've been sick or unwell.
"I don't know what that's like – touch wood I'll have another good pregnancy!"
Meanwhile, Kim, 35, described her pregnancy as, "awful", and said: "I just don't think pregnancy and me really agree with each other. I'm just being honest. I hate it.
"I've heard stories forever about how amazing pregnancy is from my mum and Kourtney and that's just not the case for me and I'm not going to sit here and lie and act like it's the most blissful experience. It's awful."
Just like glam Kim, Billie, 25, says it's important to still feel sexy as a mum, but thinks the Keeping Up With The Kardashians star sometimes goes too far with her wardrobe.
"Sometimes she looks really nice, but sometimes I think it's a bit too much. There are ways of dressing your bump – you want to be more comfortable and casual."
Billie has just released a Christmas clothing collection - available now from www.inthestyle.com.
Read more from Billie in the new issue of Reveal magazine - OUT NOW!
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