I stay away from parties for that very reason: I don't feel comfortable in crowded places.

BTW, this discomfort has nothing to do with claustrophobia either. I actually *like* small, tight spaces.

I just get overwhelmed with too many people nearby. I break down internally. I'm not sure what it is that I dislike. It think there's just too much to process at once -- too much stimulation.

IMO, every person has their limit in terms of how much stimulation they can handle. Your limit is probably low like mine.