Suggest Treatment For Severe Cough

Hello, I have been coughing for 3 weeks now. It started from the chest (no as usually from the running nose of soaring throat). It s a kind of spasmodic cough, which comes as attack and at a time of attack I am short of breath. I also feel now as if my throat has been squeezed, I can t really breath freely as I used to. I visited 2 different doctors, they found my chest and lungs okay, sounding good. Prescribed a cough syrop and told not to worry. But nothing helped and I still have those awful spasmodic cough attacks and at a time of the attack i can t really breath, i am short of breath. This scares. Should I visit one mre doctor? What should I do? Please help!