Acting NT even though it feels rude

When I started to realize that I felt really excluded, I noticed that people aren't really as I thought they were supposed to be. I felt like I was doing "social" wrong. For example, in high school I would maybe speak to someone in class or I became friends with them the year before, but I noticed they would just ignore me after. It made me feel bad, but I thought that's how you're supposed to act. So I started to pretend I don't know people when I'm walking in the halls. I got really negative responses, of course. This is just an example.

I knew some girls that I would examine for behavioral ideas and copy them. I noticed some things I thought might be impolite were actually expected of you if you want to be seen as "normal". I get so frustrated about social rules sometimes because they're really inconsistent.

I feel as though I could be wrong about the ignoring acquaintances thing. It's just that I notice it being done to me so often that I thought it was normal or okay to do.

That's the end of my vent... I hope I'm not the only one who feels this way or has several examples.