Entertainment Tonight ET Online ETOnline.com

Sexiest Man Alive Bradley Cooper reveals a shocking past of alcohol and drug abuse leading up to a blood-addled night in the hospital which led the Hollywood star to embark on his road to sobriety.

The 37-year-old actor tells The Hollywood Reporter (on stands September 14) that he's been drug and alcohol-free for eight years, citing one of many self-harming incidents that would leave Cooper recuperating for days.

"I was at a party, and deliberately bashed my head on the concrete floor," he remembers of one particularly bloody incident. "And then I did it again. I spent the night at St. Vincent's Hospital with a sock of ice, waiting for them to stitch me up."

VIDEO: Bradley Cooper's 'Words' for His Ex-Girlfriend

Fearing he would "ruin" his life, Cooper became sober at 29.

"I don't drink or do drugs anymore," he says. "I realized I wasn't going to live up to my potential, and that scared the hell out of me. I thought, 'Wow, I'm actually gonna ruin my life. I'm really gonna ruin it.'"

VIDEO: Jennifer & Bradley's 'Playbook' Chemistry

Of realizing he had a problem, Cooper admits "Part of me believed it, and part of me didn't, but the proof was in the pudding…I remember looking at my life, my apartment, my dogs, and I thought, 'What's happening?'"