maybe it was your thinking about the exam ,that brought it on,most of our dreams are connected to our thoughts and subconscious,even though they might be crazy and you can't connect it with you.This is why our dreams can effect us or make us feel bad.
To be honest that might make sense, it really didnt set the tone for a good exam!
our dreams can be analysed ,there's many time i've dreamt and felt lousy and weird all day.
I guess. It just sucks this was on an exam day!