Oprah Winfrey is opening up about her past like never before.

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In a preview for an upcoming interview with Dr. Oz, the TV icon emotionally shares new details about her childhood and the trauma that has stuck with her throughout her 67 years on this planet.

“My grandmother and I slept in the bed together. My grandfather was in a room on the other side of the wall and one night in the middle of the night, my grandfather gets out of bed and comes into the room and I wake up and he has his hands around my grandmother’s neck and she is screaming,” Winfrey recalls.

The TV host says that her grandmother managed to push him off of her and call for help.

“It’s pitch black in the middle of the night in rural Mississippi. And she goes out on the porch and she starts screaming ‘Henry! Henry!’. There is an old man who lived down the road that we call Cousin Henry, he was blind,” she says.

“It’s the first time I’ve talked about this,” Winfrey admits. “Cousin Henry comes down the road in the middle of the night to help my grandmother, get my grandfather up off the floor. And after that, my grandmother put a chair underneath the doorknob and some tin cans around the chair. And that is how we slept every night.”

Continues the entertainment mogul: “I’m sleeping, I always slept with, listening for the cans. Listening for what happens if that doorknob moves.”

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However, Winfrey reveals that despite witnessing the traumatizing moment that her grandmother went through, she was also the victim of physical abuse from her grandma.

“As I was bringing the water back, I was, like, playing with the water with my fingers… and my grandmother was looking out the window. And when I brought the bucket in, I’m sloshing the bucket cause’ I’m a little girl and she’s like ‘Were you playing in the water? Did you have your fingers in that water? That’s our drinking water,'” Winfrey recalls.

“I said ‘No ma’am’ and she said ‘I saw you and your fingers in the water’ so she, you know, grabbed a switch and I got a really bad whipping for it and later when I put on my clothes to go to church one of the welts from my back opened up and bloodied the dress,” she continues.

Adds Winfrey: “So, my emotion now is not because I feel such deep pain about it, I just feel pain for that little girl.”

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Throughout the wide-ranging intimate interview, the 67-year-old is also candid about mental health and just exactly how it impacted the girls that attended the Oprah Winfrey Leadership Academy for Girls in South Africa.

“At one time I thought that I was rescuing these girls and doing a great service by building the school, which I still think it’s a great service,” she states.

“But girls as they were graduating — and I had 20 girls in the United States I think in 2012 the first graduating class — and out of 20 girls, five of them doctors, ended up in hospital with depression and suicidal ideations and I was distraught,” Winfrey admits.

“So imagine you know families who have one person in their family who’s mentally ill I had five at one time,” she adds.

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The entire one-on-one conversation with Winfrey is set to air on “The Dr. Oz Show” on Thursday, April 29 at 4.p.m. ET/PT.