Nope, I'm right in there with you.
I was furious with my husband a couple of weeks ago. We were at a birthday party for one of HIS old college friends - people I don't know nearly as well as he does - at a restaurant, that had a playground. I was finishing my sandwich, when the kids wanted to walk over to the play area (it's a large complex) - so he takes them over, and leaves me, sitting by myself, in the middle of a group of about 50 people - only TWO of which I knew, who were the hosts, and were obviously too busy to entertain only me. The kids could have waited two minutes - instead, it took me a while to figure out where they had gone, and I had to be all awkward so I could leave and find them. Mind you, he knew most of the people there. Grr.
I find that having something to keep me occupied helps (like taking care of the kids!) - and I DON'T mean sitting there on my phone. Ask people questions. People like to talk about themselves. To help my own confidence, I thought of professions I know nothing about, that kind of give me the creeps, and came up with a question I could ask that person. Taxidermy. How do they hide the wound? Is there sewing involved, or some kind of glue, or patches, or what? How do they decide on the pose? I've never actually talked to a taxidermist, so now I'm kind of looking forward to meeting one. Mortician. Why are people never buried in their pajamas? People always say, "They look asleep," well, why not pajamas? I've never actually asked a mortician if I can be buried in my pajamas. (Please, if there is anyone on here who knows any of these answers, Don't Tell Me! Then what will I ponder?) I figure that if I can come up with something to say to a taxidermist or a mortician, after they answer the dreaded, What do you do? question, then I can probably talk to anybody. (Also have an answer if they ask you what your favorite part of your job is...)
Not that I'm 100% confident, but that sort of mental game helps, and gives me something to think about, other than being nervous.
Also, if you are in a group, and the conversation is swirling around you and you don't know what to say or add to it, it's okay to say, "Excuse me, I need to go get a drink refill," or lean in and confidentially ask, "Do you know where the ladies' room is," or just say, "Excuse me," and step away, and go talk to someone you know, or go "check in on the kids" on your phone, or actually go to the ladies' room, or even step outside for some fresh air.