For seven seasons, Jon Hamm boozed it up on camera as hard drinking adman Don Draper on AMC’s Emmy-winning drama Mad Men. And that kind of behavior spilled over into his personal life as well.

“I like whiskey — bourbon, rye, all that stuff,” he said last year. “Sometimes I like it too much.” What a difference a year makes. After spending 30 days at a rehab center for treatment of his alcohol addiction, the 44-year-old actor is clean and sober and has been following a 12-step program.

jon hamm 'mad men'
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Jon as Don Draper on 'Mad Men.'

“Jon’s going to meetings at least three times a week, calling his sponsor every day and meditating,” an insider tells 'Closer.' “He says he hasn’t felt this good about himself in years.”

Related: 'Mad Men' Star Jon Hamm Completes a 30-Day Rehab Stint for Alcohol Abuse

His first step toward a new life had been a long time coming. “Jon has known he’s had a problem with drinking for many years, but it wasn’t until the past year that he finally decided to get serious about sobriety,” a friend of Jon’s longtime girlfriend, Jennifer Westfeldt, says. “He was sick and tired of waking up hungover. The blackouts were more frequent, and he said he’d finally hit bottom.”

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Jon and Jennifer in December 2014.

That’s why he headed to Connecticut’s Silver Hill Hospital. “He went to rehab on the East Coast because he had a friend who’d gone there,” says the insider. “He didn’t want a ritzy rehab where they just take your money and pamper you.”

To read the full story on Jon, pick up the new issue of ‘Closer Weekly,’ on newsstands now!