11/28/2012 09:07 am ET

Thomas Beatie -- AKA the Pregnant Man -- On Oprah's 'Where Are They Now'

Four years after he first appeared on "The Oprah Show," "pregnant man" Thomas Beatie says he is "surprisingly fantastic" despite the many changes in his life.

Thomas was seven months pregnant when he and then-wife Nancy appeared on "The Oprah Show" in 2008. The couple allowed "Oprah Show" cameras into their ultrasound appointment and shared with viewers their joy. Following the birth of their daughter Susan, the pair had two more children.

Today, Thomas is in the middle of divorcing Nancy and is now a single father to Susan, Austin and Jensen. Although he says he is devastated by the loss of his marriage, he says that splitting up was the right thing to do. "We tried very hard to make it work," he tells Oprah on "Where Are They Now," "but ultimately the best thing for the both of us and for the children at this time was for us to go our separate ways."

Thomas says that raising three children alone is a challenge, but one he welcomes. He also says that he does not see himself as both a mother and father. "I see myself as a father who gave birth," he says. "Susan, Austin and Jensen call me 'Daddy.' And that is my name. I'm not Thomas anymore -- I'm 'Daddy.'"

After losing everything in the 2010 Flash Crash, Thomas gave up day trading in the stock market and is now focusing on public speaking. He has also written a book and is teaching tae kwon do to children.

Meanwhile, he has had gender reassignment surgery and now has a penis. He started dating again and is now in a relationship with a woman named Amber, whom he met at his children's school.

"There's just so many special things about him," Amber says. "You know, seeing him with his kids was a wonderful thing for me. And then just being around him. He's just kind and fun. He's funny. He makes me laugh. And we just have fun together."

Thomas says his life today is fantastic. "You know, 10 years ago I wouldn't have imagined I'd be in the place that I am right now. That I would have been a pregnant man.... All of the million little decisions I have made up to this point have created these [children's] lives and they are everything to me. Through all of this I've determined that that's my meaning and purpose in life: to usher these human beings into this world and make sure that I'm always here for them."

Tune in to "Oprah: Where Are They Now?" Tuesdays at 10 p.m. ET on OWN.