Hi -- I wrote the following for someone else awhile back. It seems to me that it might be of some use for your situation too, because, when my little guy started throwing up around 9 months of age, our pediatrician thought it was an ear/sinus infection too. We went through 3 rounds of antiobiotics before I said "enough! What else could it be?" So, here you go:
Food allergies. Or rather, a food intolerance. I say this because my son (almost 3) threw up a heck of a lot (about 3 times a day) and it took us months to figure it out. It took us months because food allergies don't typically manifest themselves as vomit, so it wasn't a food allergy, right?! It turns out, he has an intolerance to wheat (which he'll hopefully outgrow), along with some real food allergies (nuts and some others). When we began removing food from his diet, I only removed wheat to humor the doctor. Of course it wasn't wheat! He ate wheat 3 meals a day (bread, pasta, crackers, cookies, etc.) I did the food test (remove and re-introduce) 3 times because I couldn't believe it. Wheat -- he thew up. No wheat -- no throw up. I strongly suggest you remove things from his diet for that it could be for 5 days, and begin reintroducing them one by one in 3-5 day stretches. Things like wheat, eggs, dairy, etc -- I know, big, in everything you eat foods, so it will be a pain in the neck. But, it won't last forever. If you find it IS wheat, the initial home conversion is also a pain, but, now it's no problem. There is lots of info on the internet. I got a cookbook, there are many gluten-free foods out there (we buy crackers, pasta, graham crackers, animal crackers, fish sticks, chicken nuggets, panko, pretzels, and make our own flour blends, in order to make his own bread. But you can buy flour blends and pancake mixes). It's expensive, so we still eat the regular versions of those things, while our son eats the gluten-free. But he doesn't throw up, he doesn't have celiac disease, and he feels much much better. Good luck.