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'

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.”

jon hamm and jennifer westfeldt

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!