Just curious to know about how many non-single men here do these things?

I have a long-term girlfriend that I find very attractive and who has a really high sex drive, but for some reason I still can’t shake off that urge to want to fuck other girls (even those that are much less attractive than she is).
I don’t crave sex with her as much as I should even though there’s never a shortage of it so a part of me feels that this is really wrong.

Am I a weirdo or am I not the only one here like this?