What Causes Constant Vomiting And Green Mucus In Eyes Of An Infant?

my son is 4 months old and for the past week he has been vomiting constantly at least 3 times a day the first day it was 10 times. the following day he had direah which cleared up after two days his stool is harder now but still very light yellowish color. he is only eating 2 oz at a time and still vomiting. not spit heavy heaves and it keeps up till hes totally empty. he moans like he is in pain not whimpers or crys or fussieness actuall moans and now as of yesterday he has green matter (mucus like) stuff comming out of his eyes. hes been to the doctor twice and hospital once he had his blood drawn and an x-ray so far. could you please give me some ideas of what this could be.