Why Do Men Check Out Other Women?

Why do men check out other women while they are seeing someone?

I really don't understand! Its honestly hurtful, but I'm afraid to say something about it. I don't want him to think I'm being crazy or jealous.

I noticed him doing it a couple times but the most recent time hit me like a sack of bricks.

It happened a week ago and it has been eating away at me since. Every girl I see near him my body enters a state of numbness. Its weird.
Why Do Men Check Out Other Women?
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