Jo Dee Messina will soon be a mom. The singer tells People.com that her unsuccessful attempt to lose weight led to her discovery of her condition. She explains that despite her efforts she just couldn't drop the pounds. That's when she decided to take a pregnancy test and found out she and husband Chris Deffenbaugh are expecting their first child. Messina says she's in her third trimester now, and that she and Deffenbaugh are having a boy. The couple just celebrated their first wedding anniversary last week. The 38-year-old performer says she's still working out, and even plans to run a five-mile race on Thanksgiving Day, noting, quote, "I'll be eight months pregnant and running." Messina notes that she also intends to get right back into shape after giving birth. After her son arrives, Messina doesn't seem to planning to slow down. She's scheduled to shoot a video for the song "Unmistakable" just six weeks after her child is due, and she's intending to go on tour next year -- with her little one in tow. While Messina admits it might be a bit of a challenge to have a baby on board, she hopes to get a little advice from fellow country music moms Sara Evans and Martina McBride as she begins her trek.