Whooping cough doesn't have to be a severe cough - it is more likely a persistent cough - often with vomiting afterward and the 'whoop' sound.

My friend who did have whooping cough in January 2009 was misdiagnosed since about November 2008 - she was told at first that it was asthma but when the asthma meds were not helping she went for another opinion and was finally tested for whooping cough and it was positive for both herself and her 2.5yr old son.

I am not saying that it is definitely whooping cugh but I would rather be tested and know rather than not IYKWIM