Britney Spears on Anxiety: 'I Turn Into a Different Person. Bipolar Disorder.'

Fame isn't easy for Britney Spears. The pop princess, who has been in the spotlight since her "Mickey Mouse Club" days, suffers from anxiety.

How does she manage? Britney relies on what she calls her “alter ego” to deal with the pressures of being an international superstar.

In her E! documentary “I Am Britney Jean” she explained, “I have always been kind of shy, since I was a little girl. It's who I am to be modest, so I really can't help it.”

Spears, 32, continued, “It's almost like it's my alter ego when I get on stage… I turn into this different person, seriously. Bipolar disorder.'”

The documentary chronicles Brit's extensive preparation for her two-year residency at Planet Hollywood in Las Vegas, which kicks off on Dec. 27.

Looking back at the media frenzy that surrounded her a few years ago, the “Work B**ch” singer said, “There was a time when I couldn't leave the house without about 20 cars following me. It was a very difficult time for me… I felt really alienated. They [the paparazzi] kind of eased up after I didn't come out of the house for like two years.”

The singer also made headlines with her comments about sex. She explained, "I love sex, I think sex is great, but I feel a little different about it now that I'm older. Sometimes I feel like I'm 20, sometimes I feel like I'm 50."

"Extra's" Mario Lopez recently sat down with Britney to talk about potentially retiring after her Las Vegas residency. Watch!