My 3 yo is suffering from a stomach ache and she threw up last nite. she feels sick and is warm. she had slightly irregular bowels.

Virus?: The most common cause for the symptoms you are describing is a virus. The most important during this time is too make sure she is not getting dehydrated. If she is able to drink and make a normal number of wet diapers (or go to the bathroom to urinate if she is potty trained), this is a good sign. She may not want to eat much, but in the short term that is ok. If gets worse, go see doc.