Cough lasting for 3 months. In throat.

Since last 6-7 years I've been battling a cough that starts after i get soar throat and cold, once it starts it stays for 3 months and no medicines have any kind of effect on it. So far i have visited so many ENTs and Allergy specialist and everything. Loads of Xray MRI CT scan Andoscopy of chest throat nose, nothing was found. Then one ENT gave me Histaglob injections, it prevented the cough from coming back for 2 years, then i had to take it again and it worked for another 2 year, and now i am taking it for the 3rd time. I am wondering if there is a permanent solution and to know exactly what's the problem and if I can do something to prevent it. When the cough happens it's unbearably difficult, i can't sleep laugh eat, i lose 3-4kg of weight, pain in my guts from coughing, my throat gets rashes and is in constant pain, my voice nearly goes away, and cough has different pattern, for few weeks it will come from guts, then it feels like coming from chest, then irritation in throat.