He continued: "I'm emotional, but I'm emotional in such a happy and positive way. I'm like the happiest and healthiest I've ever been in my life and that means the world to me."
Underwood opened up on how he knew he had to tell the truth when felt death would have been a better option than coming out.
He said: "I got into a place for me in my personal life that was dark and bad. I can list a bunch of different things, but they'd all be excuses. But I think overall, the reason why now is because I got into a place where I didn't think I was ever going to share this. I would've rather died than say 'I'm gay.'
"And I think that was sort of my wakeup call."
Asked if he had considered self-harm, Underwood said: "Yeah. There was a moment in LA that I woke up and I didn't think I was going to wake up. I didn't have the intentions of waking up, and I did. And I think for me, that was my wake-up call of like, 'This is your life. Take back control.'"
Underwood also apologised to his former partner Cassie Randolph, whom he had met on The Bachelor, after she had filed a restraining order and accused him of stalking and harassment after they split during the summer of 2020.
He shared: "I'd like to say sorry for how things ended. I messed up. I made a lot of bad choices.
"If I'm being honest, I loved everything about her and it's hard for me to articulate exactly what my emotions were in going through with that relationship with her was, because I obviously had an internal fight going on.
"I would just say that 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."
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Helpline: 1737
If it is an emergency and you feel like you or someone else is at risk, call 111.