See I am hit and miss with this type of stuff (undiagnosed but I suspect it).
Baby shower, yes if I know everyone. Sitting in someone's house with people I know drinking tea and chatting, fine, quite enjoy it now and again. Where I only know one or two people and it's someone's house I don't know, no, decline.
Same with wedding. Family where I know lots of people, yes, fine. Friends where we know them and maybe a couple of others. Not great but I'll latch on to the people we know and have an excuse ready (babysitter).
Nights out. Once a year really. Ok with that but define wouldn't want it to be a frequent thing. But once I reach that point where I have had enough, I want to leave immediately and can get a bit panicky and upset about the time it takes from me knowing I'm done to actually getting home although I'm usually drunk enough to cover it up. I prefer the odd night in with a few friends that I feel comfortable with. Unfortunately I now feel awkward around a few so called friends and try to just avoid them which is hard when you are sitting around the same table. They always know when I'm being 'off' despite me thinking I'm hiding it well. I find the group size is always too big for me around and it gets too loud and chaotic. We were at a restaurant last year and I spas sat next to my good friend and she was being really really loud and I was struggling to cope with it so I asked her to be a bit quieter and she loudly declared that no she wouldn't.
I always leave with the first people to leave and feel hugely relieved even if I'd had a nice time.
I have a Christ6meal coming up soon. I arrange it and have always enjoyed it as we have the meal, few drinks then go home before midnight. This year though I'm not looking forward to it as there has been a bit of a split on the group and there are some I can't be bothered to make conversation with, and this WILL show no matter how hard I try. We are going back to a friends after which is fine as we did that before and there were only 4 of us so all good but this time there may be more, one will probably be the one I don't want to talk to and and now another is saying we should also meet before the meal as well which I agreed to but actually I don't want to. It will. Make the night too long, I'll reach my limit earlier and I don't want to start the evening earlier than we are (7.30). She is picking me up though so it's awkward. Unless we can get the others to say they won't be ready earlier as well. That's going to be my reason.
I hate shopping with other people. I Don't like going on my own, but I also don't really get much out of it with others either. 
I only go when I need something but it took me years to be able to go anywhere like that by myself.