Men (well, straight men, anyway) are biologically wired to react differently when interacting with women, versus with other men. In each individual person, the extent and nature of that difference is unique, but it's not an unexpected thing. So that fact that he's doing this is not unusual.

And the fact of the matter is, you are being jealous.

Whether you're being justifiably jealous is something else; if his interactions with women are such that they are hurtful to you, there's an issue that needs to be resolved, whether it's his fault, or yours, or a combination of both.

Why does it bother you that he interacts with women this way? Is it because you think he's interested in them? Is it because you think they are interested in him? Is it because you think it's a sign that he's less interested in you than he should be?

It's important to understand the underlying cause of your feelings.

Also, does he behave this way with all women, or just a certain type (age group, level of physical attractiveness, what-have-you)? Because if he's this way with all women, from young to old, attractive to non, then it's a very different underlying cause, as opposed to if he does it only with a particular subset.