Chronic Dry Cough

Hello hi, I am having constant dry cough on and off, mostly whole year...like a TB patient. I tried every medicine and anti-biotics, on the counter etc...nothing helped, just a temporary relief. On the contarary, I went to the lung specialist, I forgot technical word for those Doctors. Anyways, I had all kind of tests and X-rays...everything came out negative. I don't even have Asthma. It is a mystery what kind of cough I have...yaa, I can't bear a smoker around me thats for sure. Also, something is bothering me in the throat which is stuck there and kind of itching is there in the throat. Please help if somebody has any suggestions! I sometime can't talk over the phone as cough starts then it is hard to stop. Is there any cure? sushila9