The 19-year-old reality TV star -- who was previously married to co-star Corey Simms, the father of her two-year-old twin girls Aliannah and Aleeah -- is now engaged to Jeremy Calvert and expecting her third baby, Us Weeklyreported Wednesday.
"Leah just got engaged over the holidays and is pregnant with another child," a source told Us. "She is so excited!"
While it hasn't been shown on Teen Mom 2's second season -- which premiered on MTV last month with Messer and Simms still together -- yet, Messer filed for divorce in April 2011 less than six months after the couple tied the knot in an October wedding which aired on MTV in March 2011 on the show's first-season finale.
Messer told Us last month that she and Calvert were talking about getting engaged.
"We have a really good connection," the teen mother said.
"It's different from Corey and my relationship, because we were kinda like forcing it... With Jeremy, you know when you're supposed to be with somebody and you're not."