I'm upset that my fiancee is getting drunk tonight
Why are you upset? He is just trying to enjoy himself?
He's making a poor impression on my friends and it's embarrassing for me.
I'm sure you must be very embarrassed by your boyfriend's drinking. He should be able to control his behavior and not get out of line. You should have a discussion with him about having more self control with alcohol.
Nah forget it, more drinks coming.
Encouraging the drinking will probably just make the problem worse. You should tell him that you are upset so he knows that he should just skip the drinking at the next function that you go to.