EXCLUSIVE

Roberto Esquivel Cabrera claims he was tormented by U.S. prison guards because of his enormous penis.

Turns out Cabrera is a felon who served time in a Mississippi pen for entering the U.S. illegally. The penalty was especially harsh because he had been convicted of felony forgery years before in the U.S.

During his prison stay between 2003 and 2011, Cabrera filed a lawsuit claiming mistreatment. He says in handwritten documents guards treated him like a freak, demanding to take pics of his 19-inch penis, which they cruelly nicknamed "Anaconda."

Cabrera says a female guard became a Peeping Tom as he changed his clothes. He says gay prison guards would grab his penis while searching him ... he did not explain why he says they're gay.

Cabrera goes on to say he was disciplined once when his penis was hanging out of his shorts ... something he says was beyond his control.

He says in the docs he was denied special underwear which he says he needed because of his condition.

The prison guards tell a different story, claiming he would masturbate in his cell and would often expose himself for shock value.

The lawsuit was dismissed.

Roberto was released in 2011 and sent back to Mexico.