Madonna (search) is worried that her secret wasn't juicy enough. When her new documentary, "I'm Going to Tell You A Secret (search)," premiered in New York, she said she was nervous the audience wouldn't like it.

"It was like, 'Oh my God, oh my God, I hope I did the right thing. Oh, that scene is too long. Oh, that's too short. Are they going to get this part? Are they going to like this? Oh, they're going to think it's boring!' Just worrying the whole way, biting my fingernails off," she told ABC News Radio.

The documentary, which aired Friday on MTV, is a behind-the-scenes look at Madonna's "Re-Invention Tour." It follows the pop icon all the way from dancer auditions to rehearsals, a visit to Israel and the final show.

She worked on the film for a year. Despite her nerves, she said she thought the fans and contest winners selected to attend the screening liked it. "When I got to the end of it (the screening) ... I could feel that people enjoyed it," she told ABC. "That was a huge relief for me," she says.