Jessica Simpsonis fit and fashionable!

The singer, 39, pulled-off the chicestday-to-night outfit comboin NYC on Tuesday, after revealing on Instagram that she lost100 pounds in six monthsjust a few hours before.

Simpson first stepped out in a bright orange peacoat, layered over a black long sleeve top and paired with oversized sunglasses, black stilettos and a velvet and leather tote bag. The designer posed next to aMacy’sstore sign for anInstagrampicture that perfectly captured the fall outfit.

“I am feeling very blessed and inspired getting to shop and work at the same time with @macys,” Simspon (whose self-titledclothing and accessories lineis sold at the department store giant) captioned the post.

Then later that day, the “With You” singer slipped into a curve-hugging little black dress, which featured ruching, a plunging neckline and a hint of lace detail.

Raymond Hall/GC Images; Gotham/GC Images

Jessica Simpson

“NYC Ladies’ Night,” she wrote in a sexy Instagram post.

Fans celebrated Simpson’s weight loss — and her fashion-forward back-to-back looks — in the comment section.

“You look like such a boss,” one user wrote. While another sweetly commented, “You look great these days! Not that you didn’t before.”

Raymond Hall/GC Images

Jessica Simpson

Just hours before sharing outfit pictures, Simpson announced on Instagram that shelost 100 poundssix months sincewelcoming daughter Birdie Mae, on March 19.

Jessica Simpson/ Instagram

Jessica Simpson

“My first trip away from #BIRDIEMAE and emotional for many reasons, but so proud to feel like myself again,” Simpson continued. “Even when it felt impossible, I chose to work harder.”

On Thursday, the star posted anadorable videoof Birdie with husband Eric Johnson and their older children,Ace, 6, andMaxwell, 7. Seemingly missing her family, Simpson captioned the Instagram post, “Meanwhile, back at home,” with a crying face emoji.

A friend of Simpson tells PEOPLE that she is “doing great” after celebrating Johnson‘s 40th birthday this past Sunday “with close friends and family.”

Jessica Simpson and daughter Birdie.Jessica Simpson/Instagram

Jessica Simpson

“She’s working hard and working out and eating healthy and trying to get back in her best shape and excited for what’s ahead,” the source says of Simpson, whose upcomingmemoir is set to be released on Feb. 4.

“She’s trying to get back to her healthiest place,” the insider continues. “And she just wanted to get to a place where she feels her healthiest. She’s not focused on the number, but on feeling her best self.”

source: people.com