Kourtney Kardashian Reveals How Much She Weighs After 3rd Baby

"I'm on a workout kick," the reality star said.

"It's Monday! Ps: I'm 5 feet tall, so everyone relax I'm on a workout kick, trying to bring some Monday motivation," she wrote next to a pic that says she weights 116 pounds.

Reign Aston joined son Mason, 5, and daughter Penelope, 2, late last year and on Dec. 21, she introduced the little guy to the world.

"Madly in love with my little Reign Aston Disick," she wrote next to a photo holding his little hand.