What does it mean when you dream your fiance is cheating on you?

The dream suggests that the dreamer has doubts about either the fiance or about one's self. The dreamer could lack confidence in his/her worthiness, and that lack of confidence could be transferred to the fiance in the dream. Alternatively, the dream might refer to the fiance's other time commitments, perhaps with family or a job. Any activity that takes the fiance's time or attention away from the dreamer could appear as "cheating" in a dream.