Charlie Sheen revealed he is HIV positive Tuesday in an exclusive TODAY interview with Matt Lauer.

“It’s a hard three letters to absorb. It’s a turning point in one’s life,” the 50-year-old actor said.

Sheen said he made the announcement to end a smear campaign and extortion efforts.

“I have to put a stop to this onslaught, this barrage of attacks and of sub-truths and very harmful and mercurial stories that are about me, threatening the health of so many others that couldn’t be further from the truth,” he said.

READ: Charlie Sheen pens an open letter about his HIV-positive diagnosis

Sheen said he’s trusted the diagnosis with people he thought he could confide in, but has paid out upwards of $10 million to keep the illness a secret.

“What people forget is that that's money they're taking from my children,” he said about the “shakedowns” he has experienced. “I trusted them and they were deep in my inner circle, and I thought they could be helpful. My trust turned to their treason.”

He said appearing on TODAY will help put a stop to those payouts.

“That’s my goal. That’s not my only goal. I think I release myself from this prison today,” he said.

Sheen said he was diagnosed roughly four years ago, but doesn’t know how he contracted the virus.

“It started with what I thought was a series of crushing headaches,” he said. “I thought I had a brain tumor. I thought it was over.”

He also insisted it was “impossible” that he knowingly transmitted the virus to others. While he admitted to having unprotected sex with two people since the diagnosis, both were informed ahead of time and have been under the care of his doctor. But Sheen dismissed the idea that he engaged in high-risk behaviors.

"You're talking about needles and that whole mess? No, definitely not," he said.

HIV is the virus that leads to AIDS, which has no cure. But “Charlie does not have AIDS,” said the actor’s physician, Dr. Robert Huizenga, an associate professor of clinical medicine at the University of California, Los Angeles.

While an HIV-positive diagnosis used to be considered a death sentence, and there still is no cure, medical advancements have helped turn it into a manageable illness. However, antiviral drugs must be taken for a lifetime.

Sheen revealed he takes four pills every day, and his doctor said the main battle facing the actor is not related to HIV, but relapsing into substance abuse problems or entering into depression related to his diagnosis.

“We’re petrified about Charlie. We’re so, so anxious that if he was overly depressed, if he was abusing substance, he would forget these pills and that’s been an incredible worry,” he said. However, he said Sheen has been vigilant about his regimen.

“Magically, somehow in the midst of incredible personal mayhem, he’s managed to continue to take these medications,” Huizenga said.

Matt Lauer interviews Charlie Sheen in a TODAY Show exclusive interview. Samantha Okazaki

Sheen said he hopes by going public with the diagnosis, it will help dispel the stigma of HIV.

“I have a responsibility now to better myself and to help a lot of other people and hopefully with what we’re doing today others will come forward and say, 'Thanks, Charlie,'” he said.

READ MORE: What Charlie Sheen's HIV announcement means for his health

Sheen said he told ex-wives Denise Richards and Brooke Mueller about the diagnosis when he found out. He also shared the news recently with his oldest daughter.

“It hit her hard, but she recovered. She’s tough like her dad,” he said.

“I said, ‘I’m sorry I didn’t tell you sooner, but it didn’t seem like you could do anything for me and I didn’t want to burden you with all the stress.’ But she was a rock star about it.”

Sheen's personal announcement Tuesday renewed a spotlight on Sheen’s troubled history with drug addiction, pornography and prostitutes.

Charlie Sheen and ex-girlfriend Bree Olson on the red carpet in 2011. Daniel Boczarski / Getty Images Contributor

Sheen rose to become one of Hollywood’s best-known actors through a series of memorable movie roles including "Wall Street" and "Red Dawn." In more recent years, however, his public persona was shaped by a public meltdown during his 2011 feud with the creator of “Two and a Half Men,” the television series that helped him become the highest-paid television actor at the time. In the end, Sheen was fired from the show.

He told Lauer that his behavior at the time had little to do with his diagnosis.

“I wish I could blame it on that,” he said. “That was more of a (ste)roid rage. This was on the heels of that.”

Sheen admitted that period was not one he looks back fondly on.

“There’s a lot out there I’m not proud of. You can only hear ‘winning’ in the streets so many times,” he said. “I’ve pissed off a lot of really good opportunities.”

WATCH: Sheen reveals, 'I'm HIV positive,' paid many who threatened to expose me

But he said he’s entering a more thoughtful and reflective phase in his life.

“I’m approaching a time of more of a philanthropic approach in my life,” he said. He admitted that paying off people to keep quiet about his condition, as well as other factors, has hurt his bank account.

“It’s not great. It will be great again. I’m a survivor. I’ve been up, I’ve been down, I’ve been rich, I’ve been poor,” he said. “It’s another chapter in my life but it’s not commerce driven. It’s socially driven.”

Charlie Sheen talks about his HIV-positive diagnosis with Matt Lauer. TODAY

He said he doubts his HIV positive status will have an impact on his future career, pointing out a conversation he is having with the chairman of Sony, who he said is “excited about doing a show again.”

He also said he has several films lined up.

“Thus far, there’s been no resistance,” he said.

Sheen wouldn’t predict how the general media will respond to his interview, but expected his comments at least will dispel some of the myths written about him.

“I would have faith that it will be a lot more forgiving and a lot more supportive than some of the garbage I was reading in the last couple of days. Frankly, I don’t think it can get worse that that,” he said about tabloid stories that insisted he was intentionally infecting others with HIV. “I just thought, ‘Wow. Damn. That’s just as far from the truth as anything could be.' They’re going to reveal a whole lot of proof because it’s just not there. It does not exist.”

After hearing some of the encouraging reaction people on social media have had to his announcement, Sheen said he’d gladly “ride this wave of support.”

“If there was one guy on this planet to contract this that’s going to deliver a cure, it’s me. It’s me. Seriously,” he said.

“I’m not going to be the poster man for this, but I will not shun away from responsibilities and opportunities that drive me to helping others.”