"I wanted so badly to say, 'You guys have no idea. I'm in chemotherapy. You're assholes,"' she said of the tabloid press.
"But I was angry I even felt the need to say that. It's awful walking into a restaurant and having the whole room look at you, knowing what they're saying.
"I locked myself away until I was confident and comfortable again," she said.
Gomez said that she has been helped out in part by her friendship with pop superstar Taylor Swift, who "makes me feel empowered".
Lupus is estimated to strike some five million people around the world, disproportionately women of childbearing age, according to the Lupus Foundation of America.
While Gomez did not go into greater detail about her lupus, the disease is commonly treated with Methotrexate, a chemotherapy drug used at much lower doses to fight inflammation.
One potential side effect is hair loss. Since the episode, Gomez has returned to an active schedule. Her second solo album, Revival, comes out on Friday.
The celebrity website Popdust had initially reported on Gomez's lupus diagnosis in 2013, at which time the singer's representatives declined comment.
And while her ex-boyfriend Justin Bieber is currently experiencing his own revival in music, Gomez insists her former flame holds no bearing with the next chapter in her life.
"No," she insists. "This is my time. I've deserved this. I earned it. This is all me."
- AFP & WENN