"We're expecting!" Jessa, 22, tells PEOPLE. "We are so excited. The due date is November first, our wedding anniversary." Adds Ben, 19, "We are looking forward to being parents."
The third daughter born to Jim Bob, 49, and Michelle Duggar, 48, and her husband, the oldest of seven Seewald children, revealed their happy news as Jessa enters her second trimester. Tonight's episode of their TLC hit show 19 Kids and Counting, airing at 9 p.m., will feature a special message from the couple for fans.
"I am feeling pretty good," says Jessa. "The morning sickness was different every day. It's getting better, but I'm still hanging on to the heartburn. And I don't have any super-serious food cravings."
Before church one Sunday morning, Jessa says she took a pregnancy test and brought it in to show Ben.
"I said, 'Hey Ben, guess what? Yeah, you're a dad.' We couldn't believe it," Jessa says. "We are so excited. We have started talking baby names. It is one of those things that is so special, picking a name for a baby."
The couple revealed their plans to adopt in an exclusive at-home interview – and now say their plans haven't changed just because they are expecting a child.
"Our hearts haven't changed on adoption," Jessa says. (The agency the couple has contacted requires prospective parents to be married for two years before adopting.) "We are still making plans."
But Ben says that they are taking time to enjoy their happy news.
"We are trying to take it one day at a time," he says. "We pray every night that God helps us be good parents. We are getting advice from other parents."
Jessa's older sister Jill Dillard, 23, and her husband, Derick, 26, welcomed son Israel David on April 6 after a 70-hour labor. Jill, a student midwife, "has all the knowledge and training," Jessa says.
"I am not comparing, not worrying about what could happen, we are just getting prepared," Jessa says. "I think having this first year together to share our lives, just the two of us, has been special. We are definitely excited to be parents."
19 Kids and Counting airs Tuesdays (9 p.m. ET) on TLC.
For more on Jessa and Ben Seewald's pregnancy news, pick up this week's issue of PEOPLE, on newsstands Friday
Want More Duggars? Click here to get weekly updates on the stars of TLC's 19 Kids and Counting in the Duggar Family Newsletter.