Billy Joe Armstrong determined to stay sober

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Billy Joe Armstrong with his Green Day bandmates

Rocker Billy Joe Armstrong is committed to staying sober.

The 'Green Day' singer - who completed a 30-day stint in rehab in October - has revealed reminders of his public meltdown last year makes him feel "so sick" and he is determined to stay clean after battling addictions for almost 20 years with the help of "meditation through prayer".

The 40-year-old singer told Rolling Stone magazine: "I played onstage loaded a lot. I'd have anywhere from two to six beers and a couple of shots before I went onstage, then go and play the gig and drink for the rest of the evening on the bus. Fall asleep, wake up the next day, feel like s**t, do sound-check...it was over and over again. In that way, I was a functioning alcoholic.

"I've been trying to get sober since 1997, right around 'Nimrod'. But I didn't want to be in any programs. Sometimes, being a drunk, you think you can take on the whole world by yourself. This was the last straw. I had no choices anymore."

Billy also opened up about his drug addiction, saying: "I started combing them to a point where I didn't know what I was taking during the day and what I was taking at night. It was just this routine. My backpack sounded like a giant baby rattle [from all of the vials inside]."

The group's front man had a very public meltdown on stage in Las Vegas last September, when the group was performing at the star-studded 'iHeartRadio Music Festival', during which he screamed profanities and slammed Justin Bieber before violently smashing his guitar on-stage, complaining their performance had been cut short.

He admitted that he is very embarrassed that the video footage went viral and hasn't been able to watch it.

He said: "People will remind me a little bit. Or I'll see a photograph. And it makes me so sick. No. I can't go there. That's my last drink. Which is good - it's documented. Anytime I feel like drinking, I can think about it."