23 January 2010 (New York Daily News) -- Bristol Palin's goal? No more pre-marital sex.

The 19-year-old mom told Oprah Winfrey on Friday she's been depressed since the birth of her 13-month-old son, Tripp, and she won't make the same mistake twice.

"I just think it's a goal to have, and other women should have that goal," Palin said of her chastity oath.

Oprah said she "bristled" when she heard Palin would go without sex until marriage.

"Don't you think you are setting yourself up?," Oprah asked. "No, I don't," she responded.

Palin has been on her own with Tripp since his birth.

TMZ.com reported Palin is after $1,750 a month in child support from her hunky high school sweetheart Levi Johnston, who recently scored a huge payday with a photo spread in Playgirl magazine.

"I have a kid in my life, and it's my full-time job now," the born-again virgin told Oprah.

"I have this big, supportive family and stuff, but I just felt so alone," she said.

Her mom, vice presidential candidate-turned-conservative TV pundit Sarah Palin, said Friday "it was a shock" to find out her daughter was pregnant.

"Like so many other parents, I thought, 'not my kid,'" Palin said.