He has a girlfriend, so why does he talk to me so much?

Give me a sec , I'll text him and ask.

Why is the sky blue?


The answer is due to the way in which light is scattered. But that has nothing to do with your question.
HE WANTS TO SUCK YO TITTAYS
Or does it?

Gradually. Stop. Speaking. To. Him. Or just slowly become more and more unfriendly.

Or tell his girlfriend about it in a non-incriminating way. Talking to you doesn't implicate him in anything but if you feel uncomfortable by his compliments, just casually tell her that you two have been talking. Especially if he "actively keeps it a secret".

wants to have sex. Sad truth is that usually is the reason 99% of the time.

but I do really like him as a friend (JUST friend!) and also he is in love with his girlfriend, I know that he really is.

Doesn't matter whether or not YOU like HIM. If there is any semblance of there being the opposite case (him having the hots for you), then you should probably do what I say.

It kinda sounds like he wants to keep your friendship a secret because if she finds out then she'll have a massive problem with it. If he cared about her more than he cared about himself that would be enough for him to stop talking to you, but obviously that isn't the case. He likes the ego boost he gets from flirting with you too much to do that. If he keeps it from her then he can have his cake and eat it too.

Don't get me wrong, it's not like you're doing anything wrong. It sounds like you genuinely just want to be friends with the guy but he sounds a little selfish to me. Like, if he didn't make inappropriate comments towards you then his girlfriend would have nothing to get funny about. Do you know she's insecure and jealous because that's what he's told you? Because if so then I'm not sure I believe him - perfect excuse to not tell her about you. You're like his private little ego boost, but still in a way he can kid himself is totally innocent. I don't doubt he loves his girlfriend, I just think he sounds fundamentally selfish and a little immature.

the weird thing is his friends, who are also HER friends, know that he speaks to me. Well at least his family members and his best friend and a couple other close friends. they COULD tell her since they are also friends with her.

Whenever he compliments me I just ignore it or say "thanks".. I might be being stupid but I think it would make his girlfriend upset or at least it would make me upset if I were in a relationship with a guy and he was saying some things like that to female friends behind my back, which makes me uncomfortable. Maybe I am just a jealous person but apparently (yes, according to him) she is a jealous person. I actually haven't asked him if she "knows about me" (god that sounds sordid) but it's just I get the impression she doesn't. On one hand I don't want to lose his friendship. I honestly really like talking to him, he is a good and interesting person. On the other hand I do feel uncomfortable with him basically hiding everything from his girlfriend.

I think you should tell him how you're feeling about it all. Tell him you appreciate his friendship and like talking to him, but the fact it's hidden from his girlfriend makes you feel uncomfortable as it seems inappropriate (and disrespectful in my opinion, but that's by the by I guess). Then see what he says.