I need mommy advice:

my son is 14 months old and he has a viral infection (stomach bug) we went to urgent care after 4 days of him being sick, throwing up and not eating. it is now 6 days sick. not getting better, not eating but not throwing up just gaging and preventing him to eat. they said I have to let it run its course but how long do I go with him this miserable and not eating before they can do anything?