Are you my secret twin?

No, seriously... I'm just like you. I'm very shy (introverted). I don't have a lot of friends and my social circle continues to shrink.

I think it's great that you are going to play tabletop games. You'll probably meet a lot of really cool new people. I wouldn't worry about people thinking you're strange. If you worry too much, then you will come off strange. It'll be a self-fulfilling prophecy. So, relax and enjoy yourself. Surprise yourself.

I think you should just do it. You've been debating this for months, which tells me that you really want to go.

Worst case, you totally embarrass yourself, leave, and you never have to see those people ever again. Best case, you make a bunch of amazing new friends who will help you feel less lonely. I personally think the pros out weigh the cons.