The reality star welcomed son Saint in December

Credit: Courtesy Kesler Tran

She may be the selfie queen, but that doesn’t mean Kim Kardashian West always feels camera-ready.

“There was a moment after [son Saint was born last December] when my body was mush,” Kardashian West tells PEOPLE exclusively. “I felt like Gumby. There was definitely a moment when I looked in the mirror and I was like, ‘I am never going to be the same.’ “

Now, six months later, thanks to a “militant” diet (she follows the Atkins plan and is an ambassador for the brand) and a dedicated exercise plan, 35-year old Kardashian West – who is also mom to 3-year-old North – has dropped the 60 lbs. she gained during her pregnancy, and is closer than ever to her goal.

“I want to get back down to 120,” says Kardashian West, who says she weighed 132 lbs. last month. “My butt and my hips are the last to go, but I’m not stopping!”

Adds Kardashian West: “Anyone who has had kids knows your body changes and it’s hard to get your body back in shape. It takes so much determination and mental and physical power and energy.”

For exclusive photos and much more from Kim Kardashian West, pick up the new issue of PEOPLE, on newsstands Friday

[IMAGE “3” “” “std” ]Kardashian West has 6 a.m. workouts with trainer Don Brooks “every day when I’m home,” and eschews pasta and grilled cheese for vegetables, proteins and as a treat, Atkins peanut butter cups.

The reality star and entrepreneur admits, “everyone has their insecurities,” but says she’s pleased with how far she’s come.

Says Kardashian West: “After having two kids, and being able to get in shape and still feel good about myself, I’ve never felt better. I worked my ass off, I’ve altered my life and I’m proud of that.”

Keeping Up with the Kardashians airs Sundays (9 p.m. ET) on E!