Britney Believed Justin Was the One

N E W   Y O R K, Nov. 13, 2003 -- Britney Spears may look all-grown-up these days — but her youthful views about the lasting power of a young first love set her up for a difficult year that took her through heartbreak, acceptance and discovery.

The young pop star who was once famous for her virgin status says she now believes that waiting until marriage could be an unrealistic goal for longtime couples, but casual sex is still a no no.

"I think in reality, if you really know in your heart of heart that you are gonna be with that person, forever, and you really think that, with all of your heart, and you're in four, or five years, you know, into the relationship, I mean, stuff can happen," Spears told ABCNEWS' Diane Sawyer in an exclusive Primetime interview.

'You Don't Go Around Sleeping Around'

Justin Timberlake — Spears' longtime boyfriend from back in their Mouseketeers days — revealed his ex-girlfriend's sex status in an interview on ABCNEWS' 20/20 earlier this year.

Spears, 21, says she believed she and Timberlake had a relationship that would last a lifetime. She and the 22-year-old 'N Sync singer were together for three years before a high profile break up in the spring of 2002.

"You know, I mean, I, you don't go around sleeping around with people," Spears said. "I mean, I really thought that I was gonna be with him or the rest of my life. I did."

Spears has said she's not currently involved in any serious romance, but still leaves room for school girl crushes.

In fact, she's a little embarrassed about one.

When Sawyer asked about a framed picture of Spears and Brad Pitt, who is very taken by Friends star Jennifer Aniston, the mega star cringes.

"We shouldn't share that. I'm embarrassed," Spears said. "That's my little thing."

The First Time

Spears took command of the pop music world when she was just a teenager. Her first CD Baby One More Time (1999) sold a staggering 10 million copies. Since then, she's left girlhood innocence far behind, reinventing herself as a steamy sex symbol.

Her latest CD, In the Zone, hits stores this week and is a crucial release for Spears.

In the Zone reveals a more mature sound than the young singer's previous work and could possibly provide a bridge from her status as queen of the teeny-bopper music fans to an older audience.

Spears says her album is an expression of her love of living in the moment — or In the Zone.

Despite her steamy videos and sexy song titles, like "Breathe on Me," Spears says Zone isn't all about sex.

"It says it, that's what it says, it says breathe on me. That's it."

Spears says the high-stakes album, which follows her yearlong vacation, is close to her heart since she worked on many of the songs herself, including one she wrote by herself at the piano. In the song, "Everytime," Spears apologizes for letting someone down.

"My weakness caused you pain," she sings and the chorus rings out, "I feel so small. I guess I need you baby."

As raw as "Everytime" gets, Spears says it's the title song from the album that really reveals who she is right now.

"In the Zone is probably the one song that really states where I'm at … doing what I love to do, and dancing, and being in the zone."

Too Comfortable in Her Own Skin?

While Spears, 21, admits her highly publicized too-sexy-for-some September performances — the scantily clad performance at the National Football League's kickoff concert and the famous Madonna kiss performance at the MTV Music Awards — raised at least a few eyebrows, she's happy with them.

Then, oops she did it again on Monday, when she stopped traffic in New York City's Times Square during a live performance outside MTV's studio. The young performer donned a half shirt and very low-cut trousers that showed off her shiny purple underwear.

Spears says the outfits she wears during performances simply reveal how comfortable she is with herself.

"I feel comfortable in my skin," Spears said. "I think it's an OK thing to express yourself, and be the way you want to be," Spears said. "I mean, I wouldn't walk into a club or a party like that. But I think, you know, I think it's fine."

"You know what, when I was younger, … I used to run around my house, naked, when I was 13," Spears said. "And people, my dad would be like, I was just very like, free."

When Sawyer asks the freedom-loving pop star if she can think of an instance when she's gone further than she wished she had, Spears said "No. I don't think so."

But when she looked at a photo from a recent Esquire magazine photo shoot — where she took everything off but her pearls, underwear and shoes —her reaction changed a little.

"Now, those are a little much," Spears said.

The star explained that she allowed the pictures to be taken as she was heading out the door, following a shoot.

"And at the end of the shoot, I wanted to hurry up and go and of course they, they're like, put this on and I was like alright let's go ahead and do it and then let's jet and I didn't have approval over the thing," Spears said.

Spears admits it's one quick moment she wishes she could do over again."So that's one picture, I must say, that I felt kind of weird about," Spears said. "But hey, it's done. And I learned from it. And I'll never be put in that position again."

Spears on Zone Tour

Spears is putting her four-floor, $3.5 million apartment in New York behind her to go on tour for the release of her latest album.

Although she doesn't plan to play down her sexy sense of style while on stage, there is one part of Spears' body she's not willing to bare.

"I don't like my feet … I think every, no one, not, there's not a single person on this planet that likes everything about themselves, I don't think," Spears said. "But I do like my lips. So that's a good thing. Yeah."

Spears said she doesn't obsess about her world-famous bottom and that she only works hard on her abs of steel during tours.

Her In the Zone tour will kick off March 3. The first single of the new album, "Me Against the Music," featuring Madonna, is currently No. 38 on Billboard's Hot 100 singles chart.

Watch Sawyer's complete interview with Spears on Primetime Thursday.