jlspearsglamourbdaycake.jpgBritney Spears' little sis is all grown up ... and her daughter's no longer a baby.

Former Nickelodeon star Jamie Lynn Spears has written a personal essay for Glamour magazine about her experiences as a teen mom and about her decisions to go public with the pregnancy news in OK magazine and to retreat to a more "normal" life in Louisiana.

Spears' account starts like this:

    "It was 2007. I had been on a Nickelodeon show, Zoey 101, and after we wrapped shooting, I just wanted to go home to Louisiana and finish high school, be a cheerleader, all that. Then I found out I was pregnant [by then- boyfriend Casey Aldridge]. I was 16. I'd had one boyfriend. It doesn't make it perfect or all right. But I was judged for something that probably most everyone does. I was young. I was in love. I was like every other teenager, except I had this last name. And I made a decision that is forever my decision."

On MTV's Teen Mom:

    "When I saw MTV's Teen Mom was coming out, I remember thinking, Oh my God, I cannot wait to see this show because there's someone else out there. I mean, I feel for those girls. I've been that girl. It does show that motherhood is hard. There were so many times—especially when Maddie would get sick—when I would cry to myself and think, I really don't know what to do. It takes bravery to be a young mom, and it does take bravery to let the world watch."

Jamie Lynn's left Louisiana again, but not for Hollywood. She's in Nashville recording an album and looking forward to the next phase of her life:

    "I'll admit, I'm kind of scared; it's a vulnerable place for me. But I think 21 will be the year for me. I hope it will be. Maybe even a boy—I don't know. Six feet tall, blond, brown, tan...I don't care. I'm excited for 21. Twenty-one is just going to be fearless."