Hi.. Last month THE EXACT same thing happened with my 3 year old.. he started throwing up...threw up a couple times was fine for like 12 to 18 hours (we thought it was over) and then it would start again..Went on for a week, we tried everything, no dairy, the brat diet, everything, nothing worked! Go to Walgreens or CVS and get a probiotic, it is over the counter, the adult and childrens versions are the same.. it is in powder form. Give it to him in the morning and the evening, drop it in a cup of Gatoraid, there is no taste so he wont know its there, but encourage him to finish it! By the 3rd dose the vomiting will be gone! My pediatrician highly recommends this and to continue it for 3 days and I promise I was sceptical to, BUT IT WORKED!! When you throw up or have excessive diarreha you lose the good bacteria in your belly, so it makes it hard for your body to fight off the bad bacteria, the probiotic replaces the good bacteria's benefits until you body can produce it for itself. And with him throwing up for so long, enough time isnt passing for his body to have time to do this naturally without a little help. Please research it but I promise this will help him!!
God Bless!
Let me know how it goes! =D