Welcome to the allergy board - and sorry you have to be here.
A lot of people here will know just how you feel - when my ds was diagnosed (dairy and nut allergies) I thought I'd never leave the house with him again. He was about the same age as your ds. A lot of tears have been shed, mostly by me, and I expect he'll add his as he gets older and starts to realise he can't always have what the other kids have.
But. Well, it does get better, or at least you will get used to dealing with it and it will stress you less. Honest. Things like always reading ingredients labels and being hypervigilant about what food is around do become automatic and you will get so used to explaining to people that that will be second nature too (if they find it irritating then tough).
Having said that, parties are always difficult, esp. whilst kids are too young to protect themselves. Our strategy, for now is: if its a party being held by friends/family etc I'm just really up front and explain what the probs might be. So, I'll always bring safe food for ds, and ask that other food is kept out of reach, packaging is available for me to read and that kids don't run round w. food. Mostly, I've found people very understanding and eager to help. Where this isn't possible, or where I don't really feel I know people well enough to ask, well we don't go - or go and leave early, before food is served. It is tough but I tell myself its not for ever - as he gets older, more will be possible.
Also, many kids do outgrow even severe egg allergies eventually. Hold onto that thought.