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06/01/2016 09:40 am ET

Ally Hilfiger Opens Up About Being 'Sick And Suffering' While Filming 'Rich Girls' For MTV

No one knew the then-teenager was battling Lyme disease.

Before there were countless reality shows following the fabulous lives of the rich and (sometimes not-so) famous, there was one particular MTV series on the forefront of this television trend. "Rich Girls" only aired for a single season in 2003, but its stars Ally Hilfiger and Jaime Gleicher -- and their outrageous one-liners -- made the show quite memorable.

Back then, Ally says, she had no idea what to expect from the series. "Oprah: Where Are They Now?" recently caught up with the now 31-year-old, who says she was mostly in the dark about how everything would be portrayed on the series.

"I did not know what they were going to call the show. I did not know how they were going to edit it in the end. I didn't know how much time was going to be involved," Ally says.

There was also something quite frightening that Ally says she was equally unaware of at the time.

"I didn't know Lyme disease had got into my brain," she says. "I was physically shutting down." 

Ally details her battle with Lyme disease in her recent book, Bite Me. She explains in the above clip that Lyme had a very real impact on the behavior she displayed in "Rich Girls."

"During the show, my brain, it would almost short-circuit. Certain times, I would say things that wouldn't make any sense," she says. "I knew they wouldn't make sense, but they were still coming out of my mouth."

It wasn't just what she said, Ally adds. It was how she said it.

"My words were slurring a lot. I was not able to put sentences together properly. And my memory -- that's still a problem," Ally says.

I was outlandishly reacting and acting out. I mean, it was very strange.

Looking back at the series, Ally doesn't view her younger self as simply the privileged high schooler who was just trying to find her way through the world. "When I look at myself, I look at this ... sick and suffering little girl who is desperate for someone to help her and to heal her," she says.

After "Rich Girls," Ally continued to struggle.

"I had a nervous breakdown after the show and couldn't think straight, couldn't speak properly, couldn't function properly," she says. "I was outlandishly reacting and acting out. I mean, it was very strange. It was really not my normal behavior at all." 

Ally's father, fashion designer Tommy Hilfiger, saw his daughter struggling and took action.

"My father was scared. He put me into a hospital," Ally says. "What's really insidious about the disease is ... you look fine on the outside. You don't 'look sick.' And there are some days where you can function normally and some days where you absolutely cannot. So, it's very confusing to the general public."

Eventually, Ally was diagnosed with Lyme disease at age 21. She believes she contracted it more than a decade earlier when she was bit by a tick at age 7.

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PHOTO GALLERY
Ally Hilfiger Growing Up

"I was on antibiotics for years, which helped tremendously," Ally says. "Then I had to turn to homeopathy and natural medicine, which was fantastic. And moving to Los Angeles, lowering the stress levels, getting more vitamin D, staying positive really helps."

Through it all, Ally says she always had her sights set on one end goal that kept her going: motherhood.

"I had this hope and this vision of me possibly one day becoming a mother," she says. "I kept my eye on that for so long, even through the darkest -- really darkest -- times during this journey. And it happened!"

In February of last year, Ally gave birth to her daughter, Harley. Today, the fashion heiress says she is in a good place in her life, mentally, spiritually and emotionally.

"I am beyond happy," Ally says, "and just overwhelmed with gratitude, humility, awe, love."

Another reality-related follow-up:

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