Sitting with PEOPLE in the living room of his Florida home, the Creed frontman is candid as he talks about the hellish events of the past year.
"I'm lucky to be alive," he says about his ordeal.
Stapp, 41, made headlines in November when he released a disturbing video in which he rambled that he was broke and "under some kind of pretty vicious attack."
Things took another troubling turn when Stapp's wife, Jaclyn, told a 911 dispatcher that Stapp believed he was part of the CIA and had made potential threats about President Obama.
And so it went for three long months, as friends and family watched Stapp unravel, his behavior becoming more and more erratic.
Now in recovery, Stapp is ready to share what happened.
"I had a psychotic break that was brought on by alcohol and drug abuse," he says. "I was hallucinating. I drove around the United States for a month, following an angel that I saw on the hood of my car."
"In my delusional thinking, I thought my family was involved in ISIS, and that millions of dollars had been taken from me to support terrorism," he continues. "All of it was nonsense. I was out of my mind."
After hitting rock bottom, Stapp began an intensive program in a dual diagnostic facility. It was there that he received a surprising diagnosis: He was struggling with bipolar disorder, a condition that causes unexpected shifts in mood, energy and activity levels.
"It made sense," says Jaclyn, a children's book author who is also the founder of CHARM (Children Are Magical), a charity that benefits kids in need.
"I definitely knew there was something going on for years, but I couldn't pinpoint what it was."
Stapp admits that he was initially shocked by the diagnosis. "It was hard to process," he says. "There's a stigma associated with it. But Jaclyn kept telling me, 'Embrace it. We love you.' It became a big sign of relief, because finally, we had an answer."
Now sober, Stapp is in intensive therapy. He takes medication for bipolar disorder, works through a 12-step program, and meets with a sponsor.
Stapp tells PEOPLE that he's taking his life day by day: "Nothing is more important than my sobriety."
For much more about Stapp's condition, including details on how the singer's family saved his life, pick up the latest issue of PEOPLE, on newsstands Friday