The 27-year-old musician has admitted his dramatic rise to fame put pressures on him whilst he was on the road, and said that his arduous touring schedule meant that he "kept getting sick", which led to him facing death on two occasions.
He said: "I almost died twice. Like, literally, it was really tough. I kept getting sick, I was sick for like a year with a cold. I just wasn't really taking care of myself."
Four years after his rise to fame, the 'We Don't Talk Anymore' hitmaker has said he's cracked the code to touring healthily, and now draws "energy" from his fans when he's on stage.
He added: "Now I know how to tour, I figured it out. It took four years but [I got it]. The fans make it all worth it. When I'm performing in front of like 15,000 people, I'll sometimes even write a song on stage from everyone's - I hate using this word but - energy."
Over the years, Charlie has developed a "bad boy image", and says the style choice came as he wanted to show what an "evil twin version" of himself would be.
Speaking during an appearance on 'Lorraine', the 'I Warned Myself' singer said: "It was me thinking what would the evil twin version of me be, I was a very nice boy in high school what would the antithesis be."
Meanwhile, following his illness, Charlie underwent nasal surgery in 2018 to correct his septum, which helped him "sing better".
He said at the time: "I had nasal surgery to correct my septum, and nobody knows I had surgery. I can sing better now. I was never gonna tell anybody, but I can tell people."