Jessica Simpson is determined to burn off the baby weight and get her pre-pregnancy body back!

The 31-year-old singer/actress was spotted arriving at her trainer's house in West Hollywood this afternoon, and even though she put on an astonishing 60 pounds when she was pregnant with her daughter Maxwell, it looks like she's already lost a few since she started hitting the gym last week!

Last month Jess confirmed that she inked a $4 million deal with Weight Watchers, but according to various internet reports, she's having a very tough time getting her once flawless physique back. As if that wasn't frustrating enough, a source recently revealed to The National Enquirer that Jess' fiance Eric Johnson is turned off by her fuller figure!

"Her stomach is bloated and laced with stretch marks, and flaps of skin hang over her jeans in a post-pregnancy muffin top," the insider says. "It's got Jessica down in the dumps and wor­ried that Eric is turned off by her body."

The source continued, "When she got preg­nant, Jessica went on a nine-month food bender. She was packing away up to 3,000 calories a day and she still feels like a horse because she's breast feeding. Eric loves Jessica no matter what [but] he's sick and tired of hearing her whine about her new body ... He's turned off by her lack of self-confidence."