The Essex singer, who was announced on Tuesday as one of the acts on the bill at September's Radio 2 in the Park music festival, added that she was going public with the diagnosis in order to help her to process it, and also to show solidarity with others going through something similar.
"I just wanted to be open and share it," she continued. "One, because, selfishly, I do not talk about it enough. I'm not processing it because I'm working so hard.
"I also know how much sharing in the past has helped me with other people giving me their love and support and also their own stories. I'm an open book.
"It breaks my heart that so many people are going through so much similar and worse - that's the bit that kills me."
The performer, who gave birth to a son in 2023, went on to say the diagnosis had given her "incredible perspective".
"But honestly I need to process it and talk about it and, I need a hug," she told fans.
"You have loved me through all my good and hard times. And I don't want this to be any different."