that initial conversation is one of the most difficult, so much seems to hinder on the other person's reaction. it took a major breaking point in my relationship with my fiancee before i could admit my feelings. like your fiancee, every time i had even mentioned my feeling about the subject he would get defensive and close off. finally i realized that he either accepted me as i am, as i have him, or there was no way we could continue the relationship. surprisingly he's taking everything really well and we're doing a lot better but i'm a poly-virgin so only time will tell.
you've been with this man for awhile and care greatly for him, i'd tried to be as honest as possible about your feelings.