Kate,
The struggle is real. I have watched my wife's eyes appreciate women in a way that they have never done for me, or any other man that I am aware of. She checks them out the exact same way I do. It's kinda funny to me, in a way. I always wished we had found a way to have some fun with this similarity in our tastes.
You might be feeling that his attraction to other people detracts from his attraction to you, and that is a fair and valid feeling. You are becoming hyper-aware of his gazing and commentary (as I also became) and just now noticing things that were probably there all along. But that doesn't mean that you are any less beautiful or loveable than you would be if his eyes were focused only on you.
You'll never be able to control his attractions, but you can choose how they affect you. If you choose to stay in the relationship, I hope you can find a place somewhere between "tolerance" and "enjoyment". After all, you seem to have a common interest--maybe you can even have some fun with it (watching Mr. Universe together?).
If you don't see a path where you can accept this as a normal, even enjoyable, part of your marriage, then it's hard for me to see how you can be in a different emotional place than you are today. It's a weird place to be in, and I'm still there myself. I haven't yet found the guidebook to tell us what the right answer is.
