Willett, 27, got candid about her current state of mind on her Instagram Story Sunday, revealing — without naming Devenanzio — that she had been cheated on.
"This past week has been difficult," she began. "The person I truly loved more than anything else cheated on me and I found out and I had to leave. I don't know what else to say but I physically hurt."
Willett, who was returning from a family trip to Hawaii, continued, "I have been able to distract myself with beautiful beaches and hikes and my amazing family, but now I have to go back to reality. And if I'm being honest, I'm scared. I don't know when I'll stop hurting? When will I stop missing someone? What if I never stop replaying things in my head? When do I become angry?? I don't want to live my life angry."
"[And] you may call me a hypocrite, you may say I deserve this… and honestly that's okay," she added on a second slide. "I'm not saying any of this for you. I'm saying this for ME and for whoever out there doesn't feel like enough. I'm looking right at that person and telling them that they're beautiful and I'm here for them."
A source tells PEOPLE Willett "is having a really rough time."
"She loved Johnny and trusted him," the source says. "She is heartbroken that he could do something like this to her after all the time they've spent together."
A rep for Devenanzio, 39, did not immediately respond to PEOPLE's request for comment.
The former couple met on The Challenge: War of the Worlds, which aired in 2019.
Last week, Willett confirmed the two were "no longer together" in a statement obtained by PEOPLE.
"I've always tried my best to be an open book and after seeing everything circulate over the internet, I felt like I should let you all know that Johnny and I are no longer together," she said. "While I feel heartbroken, I'm thankful to know the truth. Johnny is someone I loved [and] respected very much and so I will be taking some time to heal and process it all."