Credit: Scott Gries/ MTV/ PictureGroup

Teen Mom star Amber Portwood is slamming two new tabloid claims that she's expecting her second child.

"The rumors are absolutely false. I'm not pregnant," Portwood, 20, tells UsMagazine.com in a statement.

"I'm working hard to be the best mom to my daughter," she adds of Leah, her 2-year-old with ex-fiance Gary Shirley. "I have no plans to have more kids anytime soon."

After several weeks of living apart, little Leah was reunited with her mom Dec. 6 at Portwood's new home in Anderson, Ind. (Portwood's former home had been besieged with photographers and curious neighbors.)

Portwood "is so excited to have Leah back!" a source told Us.