Started fridat with sore throat and no voice now coughing every minute and mucus. Cough syrup/dayquil/benadryl isn't helping. Why? What to do?

Sore throat. Probably a virus a common cold. Drink fluids and rest. Yellow or greenish drainage with a fever, think bacterial infection that needs an antibiotic. See your internist or family doctor if persistent over the next week. Hang in there.