Chrissy Metz also reveals how stepping into a fat suit forĀ American Horror Story: Freak Show made her commit to keeping off the weight

After years of struggling with diets and depression, This Is Us star Chrissy Metz looks back on her journey to self-acceptance, fame, and becoming a role model for body positivity. Subscribe now for the inside story — only in PEOPLE!

It took Chrissy Metz fearing for her life to create real change in her lifestyle and kick-start her path to self-acceptance and success.

The This Is Us star opens up exclusively to PEOPLE in this week’s issue about how a decade of steady weight gain, deep depression and rejection in Hollywood led to a terrifying health scare on her 30th birthday. Just hours before an elaborate party planned by her then-husband (whom Metz now declines to name in order to protect his privacy), she began to feel heart palpitations.

“I’m like, What is this? Am I dying? What’s happening?” she tells PEOPLE. “It was really scary — really, really, really scary.”

She skipped the bash and checked into the hospital. Doctors quickly diagnosed a panic attack and issued a stern warning about her weight, telling Metz: “You can’t continue on this path.” The frightening incident triggered an epiphany. “I’m like, ‘Oh, this is not just a physical thing. It’s like a soul/spirit/mind/body collective thing. Not everything’s connecting,’ ” recalls Metz.

Credit: Jim Wright

Looking inward, she made a vow to herself to stop allowing others’ opinions and criticism to erode her sense of self-worth. Through reading and spiritual work, she says, “I realized that … at the core of who we are, we’re these perfect beings — and we’re not taught that.”

The mental shift also had a positive impact on her physically. “I was so gung ho, I lost 100 lbs. in less than five months,” she says. “All I did was eat a 2,000-calorie diet and walk 20 minutes a day.”

Six years later, Metz says she’s kept off most of the weight (though she declines to reveal her current weight) and was bolstered along the way by another revelation on the set of her first significant role after the panic attack.

Playing big top “fat lady” Ima Wiggles on American Horror Story: Freak Show, Metz had to step into a fat suit. The experience “was sobering,” she says. “I thought, ‘What if I become that heavy and can’t walk around or get stuck in the doorframe? I was like, ‘I don’t want this for me.’ “

  • For more from Chrissy Metz on how her confidence led to the role of a lifetime, pick up this week’s issue of PEOPLE, on newsstands Friday

So, while she say she’s “never been more grounded and happy to be who I am,” Metz continues to be mindful about her diet and exercise habits, including embarking on a weight loss journey in step with her This Is Us character, Kate Pearson.

“I don’t have a weight or a size [in mind],” she says of her intentions for the role. “It’s really going to be about how I feel when I look at myself. I do want to lose weight. Physically, I really am interested in just feeling better and not having to be put in a box. I don’t want to be limited by anything.”

This Is Us airs Tuesdays (9 p.m. ET) on NBC.