Why men sleep with you and then doesn't care if you sleep with someone else? I curious?

I slept with a guy on first date yeaa I know it's was wrong but it happened then we meet for second time and we slept again together... on the second date he asked me if I want to be his girlfriend I said I had to think about that and he said no this is one time question! This part I didn't understand...
Then the next morning he was kinda angry and not very affectionate which was not case in the first time.. Then I asked this means that I can sleep with other guys he just said your lifeee...
But then I reminded him that he asked me to be his girlfriend yesterday, and he said again it's was just that time that he will ask...
Then I said oki I will ask you then and I asked him if he wants to be my boyfriend now then he said I happy with you but I don't want girlfriend now! Which is strange because he literally asked me to be?
So why to bother sleeping with me and then not care if I sleep with other guys?
Help to understand this guy mind?
Why men sleep with you and then doesn't care if you sleep with someone else? I curious?
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