K.E.
Unless he is acting sick, I wouldn't worry too much ( as a mom thats a hard thing to do). Like the other moms said it could be teeth and it sounds like a stage. Kids mostly wont let themselves starve. My little girl was and still is like that with food. She would go through a time that getting her to eat 3 bites was an effort, then she would change overnight to not being able to shovel enough food in and is hungry all the time. Dont try to force the eating issue with him and stick to his eating schedule as much as possible. Hang in there,