people can be so rubbish. He really is being strange and inconsiderate.
If i were you, i would have an hour of madness (cry,scream, hate) then get the books out and channel your rage into study time.
Last year, i heard two of my best friends being really horrible about me, and telling someone a downright lie. I cried into the blonde hair of my friend for half an hour, and managed to really get them out of my head. Had an exam in the afternoon. I managed to translate my hurt and anger into an A*.
You can really do this, just don't give in to him, you can't let him ruin your exam, this will affect your entire life, and i know it's a cliche but he really isn't worth it.
Sorry i couldn't be much help, best of luck with your exams.