I would strongly urge you to find your local Al-Anon district and attend a few meetings for support and education on alcoholism.
Your fiance has a disease and always will. There is no cure for alcoholism. He can put it into a sort of "remission," but only if he chooses. But you will still be living with an alcoholic.
Just as if your fiance were diagnosed with MS or diabetes or cancer, you would be getting yourself educated on how to coexist (hopefully in a productive and positive way) with someone suffering from one of those diseases; you need to treat alcoholism the same. And Al-Anon is the leader when it comes to support and education for those of us who live with and/or love an alcoholic.
Best of luck