My son has been wheezing and coughing nonstop for 6 days. he started projectile vomiting today. i took him to the er and they said to give him zarbees cough medicine. they tested him for covid,rsv,and influenza and they were negative. whats going on?

RSV is going around . Call the pediatrician and consider RSV testing .It is a virus s treatment is mainly supportive care but consider andinhaler if he is wheezing. https://health.clevelandclinic.org/treatment-for-rsv-at-home

Did the ER physician describe what his chest exam findings were? Was there fever? Sputum? This may be pure bronchial asthma. I recommend consulting a pulmonologist ( a pediatric one if appropriate) to get it under control if it's asthma. as prolonged wheezing can be dangerous when respiratory fatigue sets in.