I've read a couple of threads lately where the OP has described their problem & someone or other has come up with the useful advice 'sounds like depression'.
Aside from the fact that from my experience, doctors are pretty crap with depression anyway, i think thats a stupid suggestion to make the the OP. its not gonna make them feel any better, pumping drugs into their system to 'cure' depression is absolutely no long term cure, and can make people think its not their responsibility so much to overcome their problems cause the illness is being treated. also hearing someone suggest you have depression is enough to panic anyone isnt it.
OP i know how you feel. i get terribly illogically nervous sometimes, hate the prospect of exposing myself to new situations when theres loads of people, parties etc. i even start to feel physically ill when faced with things like that sometimes, more so in the past than nowadays.
i think its all about your attitude personally, i dunno how it happened but one day i just thought 'why should i have to feel like this?'. i decided i wouldnt let other peoples opinions / presence (or the thought of them) stop me from doing whati want to do, and although i still do worry about stuff like this sometimes its got alot better.
my advice would be to keep a positive attitude & take small steps to do more things that you want to do out of the house etc., make yourself face new & difficult situations and eventually they may not seem so difficult anymore. Pretend like you're confident & put on a front / show so people believe you are, and one day you'll realise youre not putting on a show anymore.
It is difficult but it really can help you to build up your confidence like that

i used to lack in motivation & all that too, but ive found that if i keep myself busy i kindve tend to forget about that now too
on the other hand, maybe it is depression or something and seeing your doctor or having councelling may help.. people are different so you need to find the best way for you personally to solve this, though i cant vouch for councelling/drugs myself cause im simply too stubborn for my own good to admit i need help from someone else, i have to prove i can do things myself instead lol
good luck OP, hope you can overcome this cause i know how horrible a situation it is to be in

xxxxxx