What's wrong with me?

Yesterday I was late to school and got asked by the teacher if I travelled to school via a personal car and I don't know why I nodded for some reason because I didn't travel via a personal car to school. After this incident my teacher thinks I'm dumb or something. It is now stuck in my brain and I can't seem to get it out... things like these don't happen to me on a regular basis. Can someone help me figure out what's wrong with me?