updated 06/07/2014 AT 6:00 PM ET
•originally published 06/08/2014 AT 11:00 AM ET
She may make wearing an itty-bitty bikini in front of all of America look like no big deal on Sunday, but being able to confidently strut her stuff on stage didn’t come so easily for Miss USA contestant Jordan Wessel.
The Miss Arizona 2014 winner – who battled stomach issues all her life – kick-started a nearly four-month-long diet and workout plan last April that resulted in a 40 lb. weight loss.
“I didn’t really know what it felt like to feel healthy,” Wessel, 20, tells PEOPLE about her struggle with celiac disease, an immune reaction to eating gluten. “My senior year of high school, my stomach was in so much pain and was affecting every part of my body.”
After keeping a food diary and realizing gluten was making her ill, Wessel “created this bucket list of all these things I wanted to accomplish” once she discovered her key to health.
At the top of her list? Modeling.
“I was always one of those people that always had a lot of friends, but I never felt like I could truly be myself because I was just all self-conscious and stuck in my own head,” she explains. “I’ve always been bigger than all my friends and all the boys.”
To help boost her self confidence and her motivation, last year Wessel signed up for a bikini competition set for July 17 and began training and dieting April 1.
“To lose all of that weight wasn’t my original intention,” she tells PEOPLE. “My main thing was that I wanted to feel confident in myself and feel healthy.”
After working with a trainer twice a day, five days a week doing heavy weight-lifting, sprints and other “high intensity stuff,” her body underwent a major transformation by the time the competition rolled around.
Now, she maintains her body with a strict diet and exercise routine that includes high-intensity interval training five days a week and yoga twice a week.
Meals include homemade “protein waffles” (half a cup of gluten-free oatmeal blended with half a cup of MuscleEgg and half a cup of blueberries) for breakfast, 4 oz. of chicken with salad for lunch and 4 oz. of chicken and steamed veggies for dinner. For snacking, Wessel eats a piece of fruit between breakfast and lunch and “some sort of protein” between lunch and dinner.
Going into Sunday’s competition, Wessel’s never felt more comfortable in her skin.
“I feel amazing. I feel confident. I feel beautiful,” she says. “If I were able to win Miss USA, that would be an incredible title. My story has the power to impact people, [but] I just need to be given the platform where I can reach more people.”
The Miss USA 2014 pageant airs Sunday (8 p.m. ET) on NBC.