Britney Spears asks "What the hell was I thinking?"

NEW YORK (Reuters) - Pop star Britney Spears plans to set the record straight about her personal and professional woes in a documentary to be aired shortly before the release of her new album "Circus" in December.

In the 90-minute film, "Britney: For the Record," Spears talks about her high-profile meltdown, which included stints in rehab and psychiatric hospital units, an ugly divorce, losing custody of her two sons and shaving her head.

"I sit there and I'll look back and I'm like: I'm a smart person. What the hell was I thinking?" the 26-year-old singer says in the documentary shot by filmmaker Phil Griffin over three-months.

In the past six months or so, Spears' father Jamie has taken over management of her affairs and helped get his daughter's life back on track. She has made guest appearances on U.S. TV series "How I Met Your Mother" and is due to release her sixth studio album on her December 2 birthday.

The album -- from Jive Records which is ultimately owned by Sony Music Entertainment Inc, a unit of Sony Corp -- marks the follow-up to 2007's "Blackout," which was also billed as a comeback, but failed to return Spears to the commercial heyday she enjoyed at the turn of the century.

The documentary, described as showing "the reality of trying to live a normal life after all that has been exposed through the media," is set to air on MTV on November 30.

"So much has gone on over the last couple of years and there's a lot that people don't know about me that I want them to know," Spears said in a statement.

"I wanted to make this film because I started to feel like I wasn't being seen in the light that I wanted to be seen in. This is an opportunity to set the record straight and talk about what I've been through and where I'm headed," she said.

(Reporting by Michelle Nichols; editing by Mohammad Zargham)