Re: three year old throwing up only at night
Take him to the pediatrian. My 5 yo did this for YEARS and it turned out to be food allergies. But it could also be acid reflux - the vomiting when he lays down is a symptom of acid reflux.
Here's our story: After reading an article on acid reflux (which she'd had as an infant) and realizing that she had several of the symptoms, I took her to the pediatrian. After listening to all her symptoms the pediatrican said, it could be AR or it could be allergies. We had her allergy tested & she was allergic to milk, eggs, pork & peas. Which explained why I couldn't find a link between foods she was eating & why she was vomiting.