Why can't one seem to forget about the past?

Remember the question I asked about the guy I was seeing?

Anyway, I had confronted him about some lies I catch him saying and there’s was a big cold between us.

I think it’s because he couldn’t fix his obvious lies and his big ego made him unable to talk to me( he switched the whole situation and he was mad at me in the end) which I call manipulation.

Or I think guys think ” Oh I already hit it so who cares” by hit it I mean had sex. But why do guys think this way ? They just want to hit a number of girls.

The thing is we were talking to each other but I wasn’t sure what I wanted, but we still end up having sex and the next day he said something like don’t tell your girl ( I was in shocked, my ego was slapped). I would of much rather him say; ” I didn’t enjoy it, go home.” But that’s what he said and my mind was on it for some time.

What I’m really asking is why do I still think about him 2 months later if:

1. I didn’t enjoy the sex.
2. He was an complete ass-hole for asking me not to tell my girl(Maybe he wants to keep his chances open with her).
3.I wasn’t sure if I was feeling him or not.

Like why do I still want his friendship :( ?