Paris Hilton has a hard time looking back on her childhood -- in fact, it still haunts her today.
Hilton, 39, is set to be the subject of the documentary "This is Paris," which will explore the heiress' past and delve into her traumas, as well as how she became the person we know her to be today.
People magazine obtained a special sneak peek of the documentary, in which Hilton discloses her negative feelings surrounding her past.
"I'm nervous. I'm shaking," she said. "It's hard to even eat, because my stomach is just like, turning. I don't know — it's something that's very personal, and not something I like talking about."
The former reality star added: "No one really knows who I am. Something happened in my childhood that I've never talked about with anyone. I still have nightmares about it."
Per the outlet, Hilton's mother Kathy Hilton and sister Nicky Rothschild Hilton will also appear in the doc.
The film was directed by Alexandra Dean and will premiere on Hilton's YouTube channel on Sept. 14.
Hilton previously spoke about the doc during an appearance on "The Talk," calling it "very therapeutic" to film.
"I became very close with the director and she really asked me so many questions," said the former "Simple Life" star. "I started thinking about my past and what I've been through and realized just how much it's affected my life and how I was holding on to so much trauma for so long."
She even admitted that she "learned a lot about" herself through the film.
"I think when people see this film, they're really going to see a different side to me than they've ever seen before," sais Hilton. "Because I honestly didn't even know who I was up until this year."