During his sit-down interview with anchor Robin Roberts that aired Wednesday, the former Bachelor, 29, was asked about his relationship with Randolph, 25, and apologized to her for "how things ended" between them last year.
"I would like to say sorry for how things ended. I messed up," he said. "I made a lot of bad choices."
Listen below to the episode of our daily podcast PEOPLE Every Day for more on Colton Underwood.
He went on to say that he had been in love with Randolph, adding, "And that only made it harder and more confusing for me."
"If I'm being very honest, I loved everything about her," he said. "And it's hard for me to articulate exactly what my emotions were going through that relationship with her, because I obviously had an internal fight going on."
Frazer Harrison/Getty Colton Underwood, Cassie Randolph
He continued, "I would just say I'm sorry from the bottom of my heart. I'm sorry for the pain and emotional stress I caused. I wish it wouldn't have happened the way it did. I wish that I would have been courageous enough to fix myself before I broke anybody else."
Underwood and Randolph met while filming his season of The Bachelor, which aired in 2019. He ultimately gave his final rose to her, though they didn't get engaged. They dated until announcing their split in May 2020, two months after she helped nurse him back to health after he contracted COVID-19.
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Things between them took a dark turn months after they announced their split, when Randolph filed for a restraining order against her ex in September, alleging that he placed a tracking device on her vehicle and that he had showed up to both her L.A. apartment and her parents' house in Huntington Beach unannounced.
She claimed that on one occasion, Underwood loitered in the alley outside her bedroom window of her parents' home at 2 a.m., and said that he started sending her alarming text messages.
In early November, Randolph dropped the restraining order against Underwood. In a statement to PEOPLE at the time, Underwood said the two "were able to reach a private agreement."
Paul Archuleta/Getty; Robin L Marshall/Getty Cassie Randolph, Colton Underwood
During his GMA interview with Roberts, Underwood expressed his regret for having "dragged people" into his "mess," specifically referring to the women on his season of The Bachelor.
"Do I regret being the Bachelor and do I regret handling it the way that I did? I do," he said. "I do think I could have handled it better."
"I just wish I wouldn't have dragged people into my own mess of figuring out who I was," he added. "I genuinely mean that. But also, at the same time that I can sit here and say I'm sorry to all of those women, I can also say thank you, because without them and without the Bachelor franchise, I don't know that this would have ever came out."
Earlier in the interview, the former football player said he's the "happiest and healthiest" he has ever been after coming to terms with his sexuality earlier this year.
"I've ran from myself for a long time. I've hated myself for a long time, and I'm gay. And I came to terms with that earlier this year and have been processing it," he said. "The next step in all of this was letting people know. I'm still nervous. It's been a journey, for sure."
"I'm emotional, but in such a good, happy, positive way," he continued. "I'm the happiest and healthiest I've ever been in my life, and that means the world to me."