I have a different take on this. I think he is being very disrespectful to you! Sure, all guys "look" and so do girls. It's the 'nature of the beast', so to say. But looking is one thing. Telling you to your face that another girl is 'hot', or you should do your hair like her or wear your makeup like her, etc., when he knows you don't like it, seems to suggest that he doesn't care about your feelings much.
You can try the "what's good for the goose is good for the gander" thing to see how he reacts, but I think before you get married you had better lay down some ground rules or you'll be sorry.
Also, and I'm not trying to imply that he may be cheating or checking out other options, but keep your eyes wide open girl, and trust your instincts. Usually if something just doesn't seem right in your relationship, it's the little girl on your shoulder trying to poke you to say, 'Pay Attention'
