"We were going to [go] all-day drinking..." the Fashion Star mentor tells ELLE of her and fiancé Eric Johnson's planned drive to Venice Beach, Calif.
"Ride our bikes, hang out. But I started feeling this overwhelming guilt. Why would I feel guilt at the idea of going out and having cocktails with my friends?"
With an inkling that something was off, Simpson, 31, took a home pregnancy test – and discovered she was expecting. Instantly, her life changed.
"I'm a free-spirited girl, but giving up my scotch? My Macallan 18? That was hard for me!" she says.
With what her ob/gyn predicts is a 10-lb. baby on the way (the same weight her former NFL-playing beau was at birth), Simpson hopes for a slightly lighter little one.
"I was only six pounds," she notes. "So maybe Eric and I can meet in the middle."