Suggest Treatment For Cough And Sore Throat

I have a very bad cough which started last saturday after 3 days of a killer sore throat.I am taking prometh/cod 6.25 at night.It lasts for about 3 hours and then I am back up again coughing to the point of feeling as if i will vomit at times.I have also very bad gas pain ,maybe from the post nasal drip?What should i do?