Why does he act differently with me?

So this guy who is a total flirt and player with everyone, pretty much told me:

1) I am different than most girls he has met/talked to.

2) He has never told anyone what he has told me.

3) I supposdely have seen a different side of him that no one has.

And has done:

1) He stops talking to a girl once he sees me.

2) He uses the same pick up line for a lot of girls (why do you hate me?/you hate me!)... but my friend thinks that he uses the same pick up just to start the conversation but he says things to me that he wouldn't say to other girls.

So overall, I have no idea how to analyze this guy. He seems like he trusts me more than most people and he talks about serious things with me but I can't tell if there is a chance he likes me. I can't tell if he is just treating me like any other girl and using his "pick up lines", just to get in my pants or if he might be falling for me.

And the thing is, is he completely different when he is with a big group of people/other girls than when he talking/with ME alone. I HATE the version of him when he with other people (he is a douche)... but when he talks to me alone, I see a different side of him. BUT when he is with other girls, he pretty much just acts like his usual self. WHY WHY WHY?

LONG ANSWERS = BEST ANSWERS