I know how it feels! Well we cannot really be sure if you truly have Avoidant personality disorder without a proper diagnosis. So you might want to get that diagnosed! It's worth it, after you get diagnosed you could get some therapy which could help you feel less like you currently feel. One thing you could do is focus on your breathing and try to distract yourself, in these big family meetings I usually try to prepare all my conversations beforehand so I won't have to make anything up!
I wish you luck for Thanksgiving!