I think what you are describing is a form of social anxiety.

I know I get anxious in social gatherings but I also struggle with some of the things you describe. I feel really insecure in social settings and if I don't find someone to talk to I end up leaving the gathering early. I don't feel that my social anxiety is extreme but it does impact me and my interactions with people. For example, I am currently in the process of trying to make more friends but I struggle with going to new settings and not know who is going to be there etc.

I know, for me, there have only been a few things that helped with my experiences. The first one being making myself go to gatherings despite my discomfort and making myself stay despite my discomfort. I've also found that finding one person to interact with and enjoy the event with helps as well. A lot of the time that person ends up being a friend but there have been times when that was not the case.

I don't know that these things will help you but with time you might be able to find things that help you cope.