Jamie Lynn Spears found out she was pregnant in a petrol station bathroom

Jamie Lynn Spears fell pregnant when she was just 16 years old. Photo / AP

Britney Spears' younger sister Jamie Lynn has opened up about the time she found out she was pregnant in a petrol station bathroom at 16.

On the premiere episode of her reality series, Jamie Lynn Spears: When the Lights Go Out, the child actress and aspiring singer said falling pregnant was the last thing she expected.

"I don't know how you can say this without feeling a little tacky," she said. "I kept actually throwing up." Her friend convinced her to take a pregnancy test.

"We didn't want to do it at home, so I went in the BP and I took a pregnancy test," she said. Needless to say, the test was positive. "I was like, 'What? What? What?'" Spears recalled.

But she says she never had any doubt about following through with the pregnancy.

"At the end of the day, I knew I had to make a decision as a young girl myself to do something that I could sleep with every night. I knew deep down that I was going to have my little girl, even if I had to raise her on my own, and that's what I did."

Admitting she "hid for three weeks in the house with two security [guards] while the story went out," Spears added "it was a real scandal situation at the time".

Nine years later, Spears has moved on from her then-boyfriend Casey Aldridge and raises her daughter Maddie with husband Jamie Watson.