As most of America has heard by now, Charlie Sheen revealed he's HIV positive to Matt Lauer on the TODAY Show earlier this morning (November 17). In conjunction with that interview, he's written an open letter to fans about the trials he went through while living with the virus for the past four years.

In it, Sheen discusses the migraines that ultimately led to his HIV diagnosis, which he initially thought was a brain tumor: "Roughly four years ago, I suddenly found myself in the throws of a seismic and debilitating three-day cluster-migraine-like headache. I was emergently hospitalized with what I believed to be a brain tumor or perhaps some unknown pathology. I was partially correct. Following a battery of endless tests, that included a hideous spinal tap, it was sadly and shockingly revealed to me that I was, in fact, positive for HIV.”

He continued, saying he started treatment immediately but also began to self-medicate with alcohol and drugs: "The personal disbelief, karmic confusion, shame and anger lead to a temporary yet abysmal descent into profound substance abuse and fathomless drinking. It was a suicide run. Problem was, I'd forgotten that I'm too tough for such a cowardly departure. Yet, despite this loathsome and horrific odyssey, I was vigilant with my anti-viral program.”

Sheen went on to say that he was honest about being HIV positive with his sexual partners, but those around him still attempted to extort money out of him: "In and around this perplexing and difficult time, I dazedly chose (or hired) the companionship of unsavory and insipid types. Regardless of their salt-less reputations, I always lead with condoms and honesty when it came to my condition. Sadly, my truth soon became their treason, as a deluge of blackmail and extortion took center stage in this circus of deceit."

He says that after years of being consistently blackmailed by people who threatened to reveal he was HIV positive ("To date, I have paid out countless millions to these desperate charlatans"), Sheen decided to take back the narrative, hence his TODAY revelation: "News Flash: This ends today. I'm claiming back my freedom. The scales of justice will swiftly and righteously re-balance themselves."

Sheen ends the letter insisting that he wants to focus on helping others living with HIV: “In conclusion, I accept this condition not as a curse or scourge, but rather as an opportunity and a challenge. An opportunity to help others. A challenge to better myself...My partying days are behind me. My philanthropic days are ahead of me.”

The news of Sheen's diagnosis comes just days before the National Enquirer was set to release a story claiming the actor had been actively "hiding" his HIV positive status from various sexual partners and "potentially spread the devastating virus to dozens of unsuspecting women," though he denies this.

Read Sheen's full open later on TODAY's website.

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