How do I confront my fiance ? I know he is bi polar

There is a chapter is a chapter dealing with what to do when your partner is in denial.

At least from my experience, love alone is never going to be enough. It might keep the relationship together for months, even years, but eventually the bipolar disorder will destroy it. With treatment and lifestyle changes, most people with the disorder can live a relatively normal life. The trick is getting them to accept treatment, learning about the disorder yourself, and you both making those lifestyle sacrifices to prevent episodes.