Caussin, 32, discussed his experience on Monday's episode of the Whine Down with Jana Kramer podcast ahead of the one-year anniversary of his sobriety.
Caussin confirmed he spent 60 days at an in-patient treatment facility in 2016 during his separation from Kramer.
He said he's been in a 12-step program for sex addiction since.
"For me, I realized a lot of things throughout my life that sex and sexual acting out was my addictive behavior, and that's where I went to hide my feelings, to run away from reality, and that was my drug," Caussin explained.
"I spent essentially 29 years thinking or living a different way. Then all of the sudden, you shock your system, you say no, you're actually supposed to think of things this way," he said.
Caussin will be one year sober as of next week.
The former NFL player said he's had some "stumbles," including relapses, in the three years since he sought treatment.
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"Relapses, yes, but no sex outside the marriage," he clarified. "I just want to be clear, there weren't any other affairs since that moment."
"It's something he should not have done," Kramer said. "Yes, it wasn't physical out of the marriage, but it was something where the action was, basically."
Kramer and Caussin reconciled in 2017 and renewed their wedding vows in January 2018.
The former "Dancing with the Stars" contestant, who is parent to 3-year-old daughter Jolie and 3-month-old son Jace with Caussin, shared an optimistic message at the time.
"I have NO clue what 2018 has in store for me but I've never been more ready to live day by day and enjoy each day as it comes for me," she wrote.
"Here's to always believing in love and fighting for it."
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