Loud coughing for 5 days sounds dry comes on in regular bouts only couple mins apart all covid tests are back negative. what could this be?

Probably bronchitis caused by a bacteria or a virus. You should see a doctor as he may require an antibiotic. Good Luck

A virtual consultation with Healthtap is available. More details would be helpful. Did the cough occur with an illness? Does your son have asthma? Bronchospasm may result in a loud dry cough. Test for Flu and consider a pulmonary test. If he had congestion and fever, pertussis should also be ruled out. For cough lingering longer than 3 weeks, consider chest imaging. Watch for shortness of breath.