Dry, sore throat after gastroenteritis, persistent cough with phlegm. How to treat it?

Hi, I have been having sore throat and dry and sometimes phelgm cough, after an episode of gastroenteritis(lasted a week). The sore throat and cough have not gotten better for 2 weeks+. There is phelgm sometimes but not enough for me to be able to spit it out and figure out the colour. The coughing has kept me up at night and no cough syrup has done the trick. There are more episodes of coughing at night. I used to occasionally smoke(10 a week) for a period of last 8 months and am wondering if its just the cilia growing back. I haven t smoked even one cigarette for the period I am sick(2+ weeks). I am quitting completely as it isn t something I am addicted to. My main concern right now is this cough, as it does not sound like a normal cough and it feels like I am coughing through a straw while my inner chest walls vibrate hard with each cough. Thank you for all your help.