What Causes Fatigue And Vomiting?

Hello, My son who is now 2 has been to the e.r. for the past week. He does not stop vomiting. He isnt himself, is fatigued, will eat but at the end of the night throw up again. We took him off of milk, have him on the brat diet and frequent small amounts of liquid daily. He has had 2 seizures in the past with mild seizure activity involving eye movement. We are currently seeing a Neuro and had an EEG done but results will be in Monday. Hes had what we call a unicorn on the tip of his head but since he was a a baby doctors brushed it off. Im running out of what to think.