Hello, I Am A Worried Mother Looking For Answers. My

Hello, I am a worried mother looking for answers. My son is 4 years old and have had very minimal to eat since Sunday and little to drink. He complains of a stomach ache. He was having regular bowel movements until yesterday. We have been to the doctor and ER but they have no answers. The ultrasound of his stomach and X-Ray looked okay.

Please help
Sincerely, Whitney