Suggest Treatment For Cold And Fever In A Child

My son is 3 yrs and 10 mths old now. In the past few days, he has severe fever and cold. Mucus is coming out continuously. He is not having proper food for the past 2 weeks and he takes food only once or twice a day. While sleeping, he is not able to breathe properly by which he gets disturbed too. I gave MEFTAL syrup - 6ml when he had high fever and T-Minic for cold. Please suggest what medicine to give or can I consult a doctor.