Jon Hamm as Don Draper the hard-charging, hard-drinking Madison Avenue ad exec in the hit AMC series 'Mad Men.'

Jon Hamm as Don Draper the hard-charging, hard-drinking Madison Avenue ad exec in the hit AMC series ‘Mad Men.’

Jon Hamm’s stint in rehab for alcohol addiction may have led to the end of his 18-year relationship with Jennifer Westfeldt. One of the conditions of the program reportedly required him to confess his past sexual indiscretions to his long-time partner, according to a source.

Hamm, 44, quietly committed himself to the Silver Hill Hospital in New Canaan, Conn., in February.

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He emerged from the 30-day program in March pleading for “privacy and sensitivity going forward,” his rep said at the time.

A month later the first reports surfaced that their relationship was on the rocks. But the couple stayed together, and Hamm publicly thanked Westfeldt for her support.

The hospital specializes in detoxification from alcohol, prescription medication and other substances, according to its Web site.

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It also provides treatment for “mood and other psychiatric disorders as needed.” The goals of this phase of treatment are crisis stabilization, symptom reduction and medication management, according to the hospital.

As part of the program, patients are reportedly counseled to straighten out conflicts in their lives by admitting indiscretions to those close to them. The idea is to come clean and end inner conflicts that may be fueling their substance abuse and addictive behavior.

In May a year ago, rumors surfaced that Hamm and “Mad Men” co-star Elisabeth Moss were having an affair. The rumors were roundly denied. A “source” told UsWeekly they were “good friends.”

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At the time, Hamm was in Los Angeles promoting his film “Million Dollar Arm.” Westfeldt, 45, was back in New York City, where she was starring in the off-Broadway play, Too Much Sun.

More rumors surfaced in July that Hamm and Westfeldt had split. Hamm was reported to be enamored with “Minions” co-star Sandra Bullock, according to tabloid reports. Denials followed, once again.

But this time there were no denials.

The couple’s publicist, Annett Wolf, released a statement on their behalf announcing “with great sadness” that Hamm and Westfeldt were separating after 18 years together. They never married.

Both said they would “continue to be supportive of each other in every way possible,” according to the statement.

Hamm has played ad executive Don Draper on the hit AMC drama series “Mad Men” since 2007. The final season aired earlier this year.

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