It's really a hard decision to make now - whether to tell your fiancee or not. Try not to rush with decisions. And as RAL said - don't drink over it!
Maybe, take some time for your feelings to settle a little bit, and look inside yourself - what you want, what makes you happy. Not what others expect you to do, not what you are supposed to do, but what makes you at peace with yourself.
It may seem hard to stay sober, but it really gives a clear vision of what's going on in life.
Hang in here)