Charlie Sheen [1] appeared on the Today show on Tuesday and revealed that he is HIV-positive [2]. "I am here to admit that I am, in fact, HIV-positive," the actor said, who added that he was diagnosed about four years ago but doesn't know how he contracted the disease. "It started with what I thought was a series of crushing headaches. I thought I had a brain tumor. I thought it was over." E! is reporting that Charlie's ex-wife Denise Richards and their two daughters, Sam and Lola, are HIV-negative [3], while People is reporting that his other ex-wife Brooke Mueller and their twin boys, Max and Bob, also aren't infected [4].

Charlie, who admittedly has a very colorful history with women [5], said it's "impossible" that he knowingly transmitted the virus to anyone else. While he admitted to having unprotected sex with two people after he found out he was HIV-positive, he said both women were under the strict care of his doctor and knew about his condition before their encounters. The actor did reveal, however, that after he confided in certain people about his condition, they tried to take advantage of him, which he says cost him "upwards of $10 million" to keep it a secret. But in spite of everything, Charlie is looking forward to the future. "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.'" Watch his admission above and the interview with his doctor below.