Try to explain it in a physical/mechanical sense - when does the pain come in relation to your biting or clenching your teeth? When your teeth make contact? When you clench? Does it happen when your teeth are not touching?
Maybe your dentist missed a root when he performed the root canal, so the tooth still has a living (and irritated) nerve.
Maybe your dentist cracked your tooth/root when he put in that filling that started the pain. Look up the symptoms of a cracked tooth/root.
Do you know what your crowns are made of? Try to list all of the metals that are in your mouth. Did he put Amalgams in your roots? Or gutta percha?