I would take him to a doctor. Whooping cough (Pertusis) has been showing up in record numbers in hospitals. For older kids and adults it is a deep cough that you cant seem to shake but for babies and toddlers could be fatal (and if he has it he will get better quickly with medicine, but if he spreads it to other kids/young children they could get very ill).
Better to be safe than sorry. I hope he feels better soon.