Wet phlegmy cough and 18 weeks pregnant

I have already consulted a doctor and they have prescribed me a pregnancy-safe cough syrup to take which I already finished. However, the cough is still here. It started when I had allergy symptoms which eventually led to this phlegmy cough. I am worried on going to the clinic again due to another wave our city is going thru. Any over the counter syrup which I can to take?