Britney Spears is haunted by an abortion nightmare — and her loneliness during the holiday season has worsened her deep despair.

“I killed my baby!” she cried during a recent emotional meltdown, an insider told The ENQUIRER.

Britney and ex-husband Kevin Federline briefly reunited during the holidays two years ago — and Britney got pregnant, say sources.

But when Britney told Kevin about the baby, he denied being the father and accused her of sleeping around — and a despondent Britney had an abortion.

Despite going through some very traumatic and public ordeals over the past few years, Britney, 28, has made great strides in 2009.

“Britney fights depression every Christmas season, but this Christmas has been one of the worst for her,” maintained another source.

For more on Briney’s emotional breakdown, pick up The Enquirer on newsstands now!