Eminem, real name Marshall Mathers, says he dismissed friends who told him he had an issue with substance abuse.
The star came clean about his addiction on his 2010 hit album Recovery.
"I don't know at what point exactly it started to be a problem. I just remember liking it more and more," Eminem says in the film.
"People tried to tell me that I had a problem. I would say 'Get that f***ing person outta here. I'm not out there shooting heroin. I'm not f***ing out there putting coke up my nose. I'm not smoking crack'."
The rapper admits he relapsed just a month after being released from hospital.
However, he says he found strength in his role as a father to overcome his problems.
"I'm looking at my kids and [realising] 'I need to be here for this'," he muses. "Coming off everything, I literally was up 24 hours a day for three weeks straight. And I mean, not sleeping, not even nodding off for a f***king minute.
"I had to regain motor skills, I had to regain talking skills. It's been a learning process. I'm growing. I couldn't believe that anybody could be naturally happy without being on something. So I would say to anybody, 'It does get better'."
The documentary also includes interviews with Susan Sarandon, Woody Harrelson and Russell Simmons and is released this month.
- Cover Media