Cough w/o phlegm 4 years old

My son has cough w/o phlegm, already talked to a doctor and he recommend to take citirizine for 5 days, its been 2 days but still no improvement, we also avoid to give my son egg and chicken. I am so worried, The doctor said that nothing is wrong with my son'a breathing its just food allergy, but still I am bothered with his continous cough. I am 12 weeks pregnant maybe the reason why I am so emotional :(#advicepls