What the hell is my boyfriend thinking?

I'm trying to decode what he is thinking. Here's the story: we've been dating for 7 mths, he has 2 clique of friends. One clique I name it FOD, the other clique I name it YY. I am not part of any of his cliques.

During the first few mths, when he went to Hong Kong with his FOD, he told them about me, so they know my presence as a girlfriend. However, he did not mention about me in the YY clique! I find it weird (don't jump into conclusions yet!)... One girl wants to hold a bday party, and jokingly asked everyone to bring their +1 (meaning bring their partners to her party). He somehow insisted that he is single. There's a lot happening in between me and my boyfriend (giving space, etc etc etc), but I will skip that for now.

Today, I chatted up with one of his friend from YY clique. She was surprised that she doesn't know my existence! All along she thought that he was single. I've asked her plenty of qns and the both of us can't understand why he is doing this. She was nice and helped me by chatting with me about my problems (I seek this form of help because I can't find other forms of help). We've thought about few possibilities about why he is doing so. I did try to talk to him about it but his reasons doesn't convince me to understand him. Say..."you don't need to know everything" etc. Now I feel like seeking a guy for help, but I have no close guys friends to talk to about this. SO I came here. Can someone decipher what he is thinking? I need a lot of help. I would appreciate it thanks!
What the hell is my boyfriend thinking?
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