And the singer - once the world's most famous virgin - said she only slept with Timberlake because she thought they would one day marry.
Britney said thet having sex did not make her a "bad person". The couple, who worked together as child stars, dated for a number of years.
Spears, 21, said, "I've always been a tomboy, I've always ended up being the man in the relationship. I know it sounds really weird, but it's very hard for me to let go and let the man take control."
Spears, who has shed her innocent image since first finding fame, recently enjoyed a brief fling with heavily tattooed rock hardman Fred Durst of limpbizkit, the band formerly known as Limp Bizkit.
Speaking about her sex life, Spears told, "As far as the whole sex thing goes, I really did think that Justin was the one I was going to marry so I did do the thing with him after three years.
"And I don't think that's a bad thing. Just because I've admitted to having sex doesn't make me a bad person, does it?"
The singer said she would not sleep with a man in the early days of a relationship, and prefers to simply kiss. She said, "When you're first dating a guy, you can't really go there with him. I think it's more sacred and special if you just kiss."
Wallpapers of Britney Spears
