Hello You are having cough for 3 months , got relief after medicine , recurs . Such type of recurring cough with impact on voice may be due to these possibilities , these include: 1 Allergic bronchitis , diagnosis can be confirmed by physical examination by a physician . In this type of cough usually patient come in contact with some allergen like , dust , mite , mold , fine dusting powder , hay , fodder , smoke. These allergen produces antigen ,antibody reaction and causes bronchoconstriction which produces cough as well as laryngeal irritation produces bad effect on vocal cord ( voice). 2 Asthmatic allergic bronchitis . 3 Laryngeal tuberculosis , diagnosis can be confirmed by laryngoscope examination . In my opinion consult a pulmonologist and get his opinion. Good luck.