O.J. SIMPSON is so determined to end his life behind bars he’s gone on a hunger strike in an effort to kill himself, The ENQUIRER has learned.

The former football star and accused killer – who is currently serving up to 33 years for armed robbery and kidnapping at Nevada’s Lovelock Cor­rectional Center – is so severely depressed he wants to “just sit down in a corner and die,” an insider revealed.

“O.J. is done,” the insider told The ENQUIRER.

“He’s dropping weight fast, and it’s scaring the hell out of his few remaining friends. He just won’t eat, and you can tell by his voice that he just wants to die. That’s exactly what is going to happen to him un­less some good news drops out of the sky to cheer him up and give him a reason to live. However, that doesn’t seem likely.”

Although Simpson's appeal for a new trial was turned down last year, he’ll still be eligible for parole in 2017. But O.J., 66, apparently has little hope he’ll ever walk out of jail a free man.

“They ain’t ever going to let me out of here,” the source says O.J. told a friend. “I’m not going to eat, and I won’t let docs at the prison revive me in any way.

“I will fight it. I used to live my way, and now I’m going to die my way!”

 The ENQUIRER reported more than a month ago that O.J.’s doctors at the prison believed he had a brain tumor that could be cancerous. But O.J. is refusing medical testing or treatment.

The source says he told a friend: “I don’t care if I have brain cancer. I’m dying anyway. I’m not letting any more doctors probe my head. My life is already over.”

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