B.C.
Stomach flu can go on for awhile.
Keeping well hydrated is the most important thing to get through it.
Pedialyte, water, ginger ale, soup broth, etc.
There's not much the doctor can do (unless dehydration sets in, and then you'll need to have him on an IV to get him re-hydrated).
Our pediatrician told us once a gut is irritated it can stay irritated for a long time after the initial source of irritation has been resolved.
Our son had diarrhea for 3 weeks.
It's frustrating, but they do get over it sooner or later.