Coughing and itchy throat while prgenant at 15weeks!

Hi Mummies, im having cough with pleghm and its itchy. Doctor has given me meds to take but i noticed for this pregnancy, everytime new medication is administered into the body it repels and takes time to settle down after a few days of trying but i decided to stop cause i can't take the constant vomiting when actually i have overcome morning sickness. Any natural remedies can share here?