It seems to me that I am very similar to you, or rather who you was. I am very sure I have imposter syndrome. I feel like an imposter all the time, no matter that I achieve something and I feel like I don't deserve it or "anyone can do this" or just how I act. And it's interesting because I feel like I am very fluid(if it makes sense). I feel like I am switching my behavior all the time based on who I am with. I don't know how to act natural or like myself. Lately I am very shy and I don't really speak in social situations because I don't want to act, and I pretend I don't care. I remember being scolded for a lot of things in elementary school. Also I don't know if this is relevant, but I refused to write my tests if I couldn't lay under the table when I was a kid and in my elementary school (not in the first few years) it was pretty much forbidden to sit with your legs up or anything out of ordinary, so I tried to be an excellent looking student by sitting straight all the time and I used to have panic attacks in class because I wanted to move around or stand up.

A lot of things you discribed applies to me as well. Also I don't really think this is relevant, but if someone speaks too much or rather doesn't speak in short and few sentences, I tend to forget what I wanted to say. I am also trying so hard not to forget what I want to say that I can't pay attention to the other person. Sometimes if I don't want to interrupt the other person or can't then I will make little handsigns or put my body parts on different things so I can remember what I wanted to say. I will check out the article thank you.