Charlie Sheen is HIV positive and has known for four years, he said during an interview on The Today Show.

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Credit: Jennifer Brett

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Credit: Jennifer Brett

PAST COVERAGE: Charlie Sheen brought his bizarre "Violent Tornado of Truth" tour to Atlanta in 2011

Sheen said he does not know how or when he was infected but did admit he has paid for sex. He was diagnosed after experiencing terrible headaches and sweating episodes. He thought he might have a brain tumor, he said.

After he learned the truth he told some friends he trusted to keep quiet but word got out. For a time he was paying some people for their silence - which he described as "shakedowns."

"Enough to bring it into the millions," he said. "That's money they're taking away from my kids. I've got five kids and a granddaughter."

As a result his financial situation is "not great," but he’s confident his bank account will improve. He said he has several potential new projects in the works.

He said he's hoping for support and forgiveness, and may use his celebrity to raise awareness and spur research efforts.

“I’m not going to be the poster man for this but I will not shun opportunities that drive me to help others,” he said.

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Credit: Getty Images

PHOTOS: Charlie Sheen through the years

Today Show host Matt Lauer asked if he was still paying anyone.

"Not after today I'm not," Sheen said. "I've released myself from this prison today."

Sheen remained in contact with some of the confidants who turned against him because, he said, he was depressed, doing drugs, drinking heavily and "making really bad decisions."

He said it is "impossible" that he infected anyone since he learned of his diagnosis. He's informed sexual partners of his condition.

"I have a responsibility now to better myself and to help a lot of other people," he said. "Others may come forward and say, 'thanks, Charlie, thanks for kicking the door open."

Sheen's doctor says while he has tested positive for HIV, he does not have AIDS and is “absolutely healthy.”

In fact, Dr. Robert Huizenga said he is more concerned about Sheen's substance use and depression.

Sheen said he still drinks but no longer does drugs, and that the “freedom” of revealing his health status may quell his desire for drink as well.

Lauer asked if he felt relieved and Sheen said: “More than I thought possible. I feel good about it.”

Sheen was in Atlanta in 2012 to film “Scary Movie 5.” He brought his bizarre “”My Violent Torpedo of Truth/Defeat is Not An Option” tour to the Fox Theater in 2011.

Before today he had not responded to tabloid reports about his HIV status.