Welcome to the Forum. It is a hard thing for most people to do, myself included. One first off has to realise there may be a problem, then one has to talk abut personal things to strangers. It is a brave, and a wise move.
I can relate almost exactly to a lot of what you have been saying. I was not quite the same, having my anxiety complicated by other matters, but remember the 'stomach issues' the peaks of worry that came by even thinking about interactions at work, extreme worry abut my boss's reactions, and not feeling able to handle even simple task involving others while at work.
My thinking was terrible at those times, unlike you I gave in to anger rather than almost crying - whch I did later on anyway when I'd tried to keep going for too long without help.
May I ask if you are seeing a doctor or psych, and if you are under treatment for your anxiety? It sounds as if it is increasing and maybe your treatment- if you are having any - need adjusting, whch happens from time to time. Sometimes medication is added to therapy, other times therapy is added to meds or the therapy or meds changed. There can be a bit of trial and error, however hopefully you will end up having more coping skills for your new job