Actor Charlie Sheen revealed on Tuesday that he's HIV-positive and confessed that he's been paying "millions" to keep his condition secret.

"I'm here to admit I am in fact HIV-positive," the actor said Tuesday during an appearance on NBC's "Today" show. "I have to put a stop to this onslaught, this barrage of attacks, of sub truths," he continued.

Sheen said he learned of the diagnosis four years ago and has since struggled to keep his condition under wraps.

Since learning that he was HIV-positive, the 50-year-old said he has forewarned all of his sexual partners about his condition.

Sheen added that he had unprotected sex with two partners "who were under the care of my doctor" and who "were completely warned ahead of time."

Asked if he has ever transmitted the HIV virus to someone else, Sheen said, "impossible."

Sheen said he sought the help of doctors four years ago, after he began experiencing "crushing headaches," migraines and extreme sweating.

"I thought I had a brain tumour, I thought it was all over," he told "Today's" Matt Lauer.

After a "battery" of tests, Sheen said doctors told him he is HIV-positive.

"It's a hard three letters to absorb," he said of the diagnosis.

Sheen paid "millions" to keep HIV-diagnosis out of media

The actor alleges that he's been exploited by others who have demanded money to "stay silent."

He said, in one case, a prostitute that Sheen hired took a photo of his HIV medication and threatened to sell it.

Sheen said over the last four years he's paid nearly $10 millionto keep those who were aware of his diagnosis silent.

Asked about his current financial situation, Sheen said, "it's not great."

In coming forward with his condition, he hopes to put an end to the extortion he's faced.

"I think I release myself from that prison today," he said.

Sheen's physician, Dr. Robert Huizenga, appeared alongside the actor during the interview and said Sheen has an undetectable level of the virus in his blood. He's taking what's known as the "triple cocktail" for his treatment.

Huizenga also confirmed that Sheen does not have AIDS.

Sheen said he is no longer abusing illegal drugs, but he does drink occasionally, which worries his doctor.

"We're petrified about Charlie": doctor

"We're petrified about Charlie," Huizenga said. "We're so, so anxious that if he was overly depressed, or if he was abusing substances he would forget these pills."

Sheen said, however, since beginning HIV treatment he has never missed taking his medication.

Asked if he plans to stop drinking, Sheen said: "Perhaps the freedom of today might lead to that as well."

Moments after Sheen's HIV admission, many individuals took to social media to express their support to the actor, which did not go unnoticed by Sheen.

"I'm going to ride this wave of support," he said.

Sheen added: "If there was one guy on this planet to contract this, that's going to deliver a cure, it's me."

Sheen’s appearance comes the day after a tabloid report that he was HIV-positive.

The actor, who has struggled with substance abuse and admitted to soliciting prostitutes in the past, was kicked off the popular sitcom "Two and a Half Men" in 2011, after an explosive meltdown. He said Tuesday that the HIV diagnosis came on the heels of that public meltdown.