Well, if something was bothering me about my girlfriend, I'd try to keep cool about is cause it might be one of those things that happen for a few days, maybe even weeks, and then goes away. I don't really like to argue about things that don't matter, so I do my best to give things time before I take action.
And the guys talking about having sex with girls thing. Well, some guys do it to show male dominance, but mostly it's to tell other guys "This girl is off limits". And then there are the ones who go around sleeping with everybody. It's our way of saying "That girl is a whore, stay away from her".