I saw a man I had a crush on before for the first time in months. I dream about leaving my fiance for him
That's a little troubling. But do you love your fiance?
Yes I do, I was head over heels
If you have feelings for someone else you should break off the engagement. It is not good to lead someone on if you are already in a relationship.
Nah it's not fair to leave him.
That's a good decision you are making, I don't believe it's worth breaking up a relationship due to a small crush. I hope you can honest with your fiance about it, in order to prevent any problems in the future.