I think I'm in a similar situation. Until a few weeks ago, I thought I was past the point of feeling loneliness because I'd been socially isolated for so long, but starting to socialize again, even if only online, got me started feeling it again. I don't really have any friends, but being around people makes me feel even more lonely, I guess probably because I see the kind of bonds they have with each other that I don't have, and am starting to wonder if I'll ever have again. I can definitely see how being around your friends would make you feel more lonely if they're talking about things they have in common but you don't share with them. I wish I had some advice to offer, but unfortunately, I don't.
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"