Suggest Treatment For Persistent Cough Causing Shortness Of Breath

i have had a cough for several months now. Have had allergy testing done - negative. Have had asthma testing done and although negative used an inhaler and nasal spray for 4 weeks with no relief. Now taking antacids morning and night and watching my diet for acid reflex sx. again with no relief from cough. the cough is worse at bedtime, when I am tired or just after eating. It wakes me at night and often makes me short of breathe as spells can last for several minutes. Help!!