Hello

I have had this same problem for most of my life. I'm very timid and shy in new situations, especially where I don't know anyone. I also feel like I don't fit in and don't belong. And then I over analyze everything, like "oh she just looked at me and scowled. She hates me. What could I have done to make her hate me?? *Runs through list of every possible negative thing about myself in head*" Then I end up feeling defensive and judged, when in reality, the person was just spacing out in my direction, thinking about how she really doesn't want to go to work tonight.
My feelings of alienation come from an emotionally abusive childhood, where I never felt like I belonged, and always felt I was being looked down upon, and doing the wrong thing. As I've learned more and more about myself, I came to realize I definitely put off a "Don't talk to me" vibe, and didn't try to initiate conversation with anyone, so naturally no one talked to me, thus making me feel more alienated.
When I realized this, I started making more of an effort to interact with people. (Don't get me wrong, I still take forever to warm up to someone new, but I do try to not look as sullen and disinterested). You don't have to suddenly become the most outgoing person in world. When you're leaving, make a comment to someone about something that happened in the class. When you arrive, smile at the people who are already there. I'm sure you don't smell, and if you're not outwardly rude or inappropriate, people have no reason to dislike you. It's all in your head

Once you start to interact with people, they're much more likely to interact with you as well. It's uncomfortable at first, but when you try and it works, it gives you confidence.
Sorry this turned into kind of a long rant, it just reminds me so much of me! Don't stop going to the group because of the other people. Think of it as "me time", relax, and enjoy your meditation!