Anyone encounter infant 3 month plus going 4 month having flu cough and fever

My LO had phlegmy cough nearing 4 months. Brought to pd and given nasal drop to ease the phlegm. Also bought the mucus suction to get rid of mucus in the nose. My LO did not have fever only alil warmer body and i wipe LO with wet wipes since its cold/ room temperature water. PD say as long as LO eat and sleep well it is fine. But since urs have fever i think its better to go to doctor.