Don’t be overly possessive or jealous
In short, the answer is don’t react. Remember that although he’s your dude, he doesn’t belong to you; you don’t own the man. Let him set the boundaries.
Studies on patterns of attraction in birds and humans show a partner’s appeal goes up once they’re coupled up versus when they’re single. It’s in our biological nature to seek out partners with desirable traits, and when we see a man who’s wifed up, our primitive brains tell us he’s a catch.
While you’d like to think that means women will back off once they find out he’s spoken for, there are some that will probably still pursue him. Take it as a compliment. You know he’s a catch—that’s why you’re with him. And if he’s a faithful dude, he won’t return pursuit.