I think he's worried he's gone down the path of "liking" this friend, and he's worried about it because he has a girlfriend and he wants to stay faithful to her.

That's what I got anyway.

I really don't know anything about this stuff, but you could just be misinterpreting it. It's normal to really want to be able to spend time with friends. Maybe she's just a new best friend to you.

But it's really only you who can say what you feel and decide for yourself.