Hello krispy 292,
My name isXXXXX you for using Just Answer.
The most important thing currently is that you get your son to eat and especially drink. You do not want him getting dehydrated. If that happens, he will require more IV fluids. Pedialite or Gatorade is truly what you need to get him to take to replenish his electrolytes. For eating try dry toast, broth or jello. He truly truly does need to get some kind of nourishment.
If he is still having a lot of diarrhea, and has had for a week, you should take him back to the doctor to get some medication to help with this.
The best way to get him to take the medicine is to mix it in something you can get him to eat, such as apple sauce, pudding or even ice cream. Hopefully, he will not notice the taste once it is mixed in with something else and you will get him to take his full dose.
Hope this has helped you with your concern. Hope your son gets to feeling better very soon. Have a great day!