I don't know if these count as "delusions", but there was one time I was convinced that everybody hated me. I thought every person I knew and every person I saw on the street was talking about me behind my back. I thought they were all making fun of me or saying how disgusted they were with me. At the same time, I thought everyone was conspiring against me -- like, they were all out to get me. I thought they were talking behind my back to make secret plans to do something to me, but I didn't know what that "something" was. My goal was then to figure out what they were going to do to me.