Jessica Simpson made headlines for doing exactly what she was supposed to do while pregnant -- gain weight.

Now that she's given birth, new reports say the singer is seriously stressing out over her multimillion dollar contract with Weight Watchers and the pressure to meet her 50 pound weight-loss goal.

In Touch magazine reports the 31-year-old singer hasn't wasted any time when it comes to shedding the baby weight -- and has already made five trips to the gym in two weeks.

"She is as focused and determined as ever," the singer's trainer, Harley Pasternak, told the magazine.

Jessica's weight has always been heavily scrutinized by the media -- from when she whittled her body down to play Daisy Duke in the 2005 movie "The Dukes of Hazzard," to the "mom jeans" incident in 2009, in which an unflattering pair of high-waisted jeans sparked international discussion and ridicule of the singer for gaining a few pounds.

Even her estimated 40-to-50-pound weight gain during her pregnancy drew criticism, but the singer chose not to let comments about her body bother her. In April, a month before she gave birth, she took to Twitter, letting fans know they should pick up her nude Elle magazine cover before it was too late:

"Last chance to see me "fat" aka PREGNANT on the cover of Elle :) I loved this shoot, only on stands for a few more days!!!"

With the constant attention on Simpson's body, it's no surprise she's reportedly stressed about trying to lose a rumored 50 pounds in just five months.

"She’s so emotional. She doesn’t want to leave her baby. Sometimes she just starts crying. It’s hard for her," a friend of Simpson's told In Touch of the multiple trips to the gym in recent weeks.

Simpson can at least take comfort in knowing she's not alone on the journey back to the body she once had. Fellow new mommy Hilary Duff is also taking a healthy approach to weight loss, telling Us Weekly, "I'm working hard and I'm doing everything I can to lose the weight the right way."

Check out these celebrity post-baby transformations below:

Loading Slideshow...
  • Malin Akerman

  • Jennifer Nettles

  • Claire Danes

    (Getty)

  • Snooki

    (Getty, Us Weekly)

  • Megan Fox

    (AKM-GSI ,x17)

  • Reese Witherspoon

    (Getty, FameFlynet)

  • Kourtney Kardashian

    (Us Weekly)

  • Hilary Duff

    (Getty, FameFlynet)

  • Beyonce

    Getty

  • Jenna Fischer

    Getty

  • Jane Krakowski

    Getty

  • Tori Spelling

    Getty

  • Natalie Portman

    Getty

  • Pink

    Getty

  • Victoria Beckham

    Getty

  • Rachel Zoe

    Getty

  • Kate Hudson

    Getty

  • Jessica Alba

    Getty

  • Mariah Carey

    Getty

  • Alicia Silverstone

    Getty

  • Alyssa Milano

    Getty

  • Miranda Kerr

    Getty

  • Emily Deschanel

    Getty

  • Penelope Cruz

    Getty

  • January Jones

    Getty

Related on HuffPost: