July 29, 2016 04:25 PM

Shannen Doherty is opening up about her fight against breast cancer and the toll it’s taking on her body.

In a preview of Monday’s episode of Entertainment Tonight, the actress breaks down in tears while discussing her appearance.

“It’s hard,” she says at the start of the clip. “I started thinking that I wasn’t going to live … I don’t look past today.”

Doherty, 45, recently shave her head as part of her ongoing battle against breast cancer, which she exclusively revealed to PEOPLE last August.

RELATED VIDEO: Shannen Doherty Shaves Her Head as She Battles Breast Cancer

While wearing a scarf over her head, the Beverly Hills, 90210 alum – who was was diagnosed in February 2015 – says, “I don’t know if I’ll ever look like me again.”

In the three-part interview, Doherty will reveal a devastating setback in her diagnosis for the first time.

“I want to believe that if I fight,” she says. “I’m gonna be okay.”

Doherty’s three-part Entertainment Tonight interview begins on Monday (check local listings).

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