Husband is addicted to flirting and talking about sex

I have been married for 14 years now and we have 2 boys. From day one my husband has been a flirter but always managed to keep it pg and some what under control. I have given into his fantasies about another women in our bed. About 3 years ago he told me a fantasies about him being with another man. Last year at a cook out with adult friends, he was introduced to a gay man by another friend of ours. After a evening of having a few drinks he slipped behind the building with this man (without me knowing until after the fact) and they had oral sex with each other. The next day he told me about it and needless to say I was not supportive. It has not happened since then but he still keeps in touch with the man from time to time. He now has this almost uncontrollable need to flirt with other women and talk about sex constantly. I Love him very much and I know that he does not want to hurt me but its almost to the point of no control for him.
What is the next step for me and how do I help him with this ?