The Irish star shared a distressing 12-minute video on Facebook telling fans that she's been on her own "for two years" and is "struggling to find the will to stay alive".
Last fall, O'Connor said in a Facebook post that she was alone and had no emotional support.
The 50-year-old Irish singer, best known for her Prince-penned hit, "Nothing Compares 2 U", sobbed in the short video as she talks about what it's like to be far away from her family and isolated because of her mental illness. She says she made the clip to show people what it's like "one of millions" suffering from mental health disorders.
"It's like a witch hunt, they are pointing the finger saying "see, see this is why", she said. "One of millions. Why are we alone?"
A source who once collaborated with O'Connor told The Post, "Whatever you think of Sinéad, she's showing courage in laying bare her problems and shedding light on the fight millions have with depression". She also encourages her fans to go and reach out to mentally ill people in their communities lend a hand.
She explains: "I hope that this video is somehow helpful..."
"Suddenly all the people who are supposed to be loving you and taking care of you are treating you like s**t".
O'Connor then called for mental health to be taken more seriously in society and for the "stigma" surrounding the illness to change, stating: "Mental illness, it's like drugs, it doesn't give a s**t who you are, and equally what's worse, it's the stigma, it doesn't give a s**t who you are".
But she adds that she intends to survive her latest crisis.
"I'm really sad, I shouldn't be here and I know I'm just one of millions. that should be our f***ing catchphrase - why are we alone?" My whole life is revolving around just not dying.
"People who suffer from mental illness are the most vulnerable people on Earth", O'Connor said in the video. "If it was me, I'd be gone". You left me to die.
Sinead - who has four children from different relationships - revealed on Facebook in 2015 she had taken an overdose at a hotel in Ireland but she was later found safe.
In a later interview in 2014, she told Winfrey that she had sought second opinions on her bipolar diagnosis, and three psychiatrists had told her she did not have the condition.