You're entirely right. I didn't think of this when he extended the invitation. I was afraid he was playing mind games and I was also feeling jealous.
I was hurt by a lot of childhood taunting and mindgames pretending to be my friend and then ditching me for someone "better" than me.
My hearing loss has also made it impossible for me to hear in groups of people; I always wound up feeling left out because I couldn't hear.
Between all of the above, I had a tremendous amount of anxiety and gracefully declined for legitimate reasons. Not enough time to enjoy a casual get together without feeling rushed to meet up.
But still, I feel dumb and naive. I don't know how to function socially in these situations.
... but when he's invited me to do something with him AND with another girl, I just about fell on my face. What does it mean when someone wants to include another person?
I think it just means that he wants to include you in his circle of friends. And whats wrong with that? You might make some new friends through him. Could be an opportunity. What have you got to lose?
It's a heroes journey, and you are the hero.
Loving Kindness Meditation will dramatically improve your spirits; give it a try for just 3 days: http://www.youtube.com/watch?v=sz7cpV7ERsM