Hello dear, I understand your concern. It may just be a chance factor that you are correlating that slapping incident with the onset of your headache episodes.Otherwise,your episodic headache where each episode lasts hours to days and is associated with nausea,vomiting or slurring of speech is very typical of Migraine .You can discuss with your physician regarding starting anti-migraine medicines like Beta-blockers,amitriptyline,flunarizine or triptans.Please try to find out if there is any trigger factor(like stress,sunlight,any food item,smoking or alcohol) which precipitates this headache and try to eliminate it from your lifestyle.I hope it helps.