EXCLUSIVE

Former wrestler Sean O'Haire had a nasty alcohol addiction he couldn't kick ... even though the WWE went to lengths to help him get clean -- including providing him years of treatment.

Sources close to the situation tell us O'Haire went to WWE-sponsored rehab six times in the past 6 years ... including once earlier this year. After he left, we're told the wrestling company made multiple attempts to get in touch with O'Haire -- but he was M.I.A.