When she took a break from the industry back then, everyone assumed she was checking herself into rehabilitation for drug use.
Selena Gomez was actually getting chemotherapy for Lupus.
"That's what my break was really about," she told the etonline, "I could've had a stroke."
"I wanted so badly to say, 'You guys have no idea. I'm in chemotherapy. You're assholes,'" she said of the rumours.
Selena Gomez "didn't understand" what was happening when she was first diagnosed with Lupus three years ago and admits she had hoped to keep the news private.
The 23-year-old singer found out she has the autoimmune disease, that occurs when the body's immune system attacks its own tissues and organs, three years ago and admits she had hoped to keep the news private.
Gomez's admittance to undergoing chemotherapy was a shock to many, as the treatment is generally associated with cancer. While lupus is not a form of cancer, or vice versa, some treatments like chemo are used to fight both.
The Lupus Foundation of America describes lupus as a chronic autoimmune disease that can damage any part of the body, including skin, joints and organs.
The 'Good For You' hitmaker said: "[It happened] three years ago... That's when I found it and I think it was just very complicated because I didn't understand and then it was something that I did want to keep private until my whole life suddenly wasn't private."
While the starlet has had to make some changes to her lifestyle, she has come to terms with the chronic inflammatory disease and feels healthy at the moment.
She told 'The Ellen DeGeneres Show': "You'll have it forever. It's kind of one of those situations. You just have to take care of yourself."
Selena decided to hit back at critics on Instagram, who bashed her for apparently gaining weight while on holiday earlier this year, because she feared people thought she had "gone off the deep end."
She explained: "It was the first time I'd ever been called fat... it was weird because it's not just 'Oh, she's fat.' It's like, 'She's a mess. She's gone off the deep end.' I'm like, because I'm on a vacation wearing a bathing suit? Actually technically that is a little too small for me, but I didn't care. That's so degrading.
"It's so annoying when I see it all over the place and everybody thinks they can bring me down. So my immediate response was I'm gonna post a picture and I'm like, 'I'm happy with me y'all'... I wasn't gonna let that be the story. That wasn't the story."