Hi, Sir I Have The Cough From A Month. I

Hi, sir I have the cough from a month. I took the treatment from different doctors but there is no improvement. I don't have any problem in the whole day, but when I wake up in the morning , the cogh starts and also I feel vomiting for half an hour. Nowadays with all this I am suffering with another problem that when a bout of cough comes , its so hard that I become unconscious for few seconds.
I have gone through blood test and x-ray test but all things are normal. I don't smoke and don't drink. I am a pure veg person. Then why can't any medicine cure my disease? Do you have any solution? Doctors have diagnosed that its because of only alergy but I don't feel so.