Metabolic Intolerance.

The vomiting, weight issues, sleep issues and abdominal pain all point to food. I'm assuming mechanical/structural issues have been checked like hernia's and blockages etc.

Food intolerances (for those that don't know) will not show as an allergy because they do not trigger an immune response, they are a metabolic incompetence.

Also keep this in mind guys, GERD is NOT a specific condition it is a symptom of something else. And vomiting is not reflux. Reflux is a normal everyday occurance that happens to everyone. We are oblivious to it (most of us) because there is no pain associated with it. When there is pain (or a complication like aperation) then treatment is necessary. When there is pain it means that there is either too much acid or a structural problem. If they have checked with a scope to rule out a structural problem, or a blockage of some sort further down then the problem is excess acid. Excess acid occurs when particles reach the intestine too large to process, so more acid is generated to break the particles down. This occurs for a whole host of reasons, and this is where a specialist comes in.

A GI is like a plummer, he can tell you if your pipes are not functioning, after that you need a better Dr.

Yes acid reflux can trigger vomiting, but vomiting itself should not always be considered GERD. And if the vomiting is occuring with force (projectlie, for example, or in large volumes), versus like a spit-up, then it should be seen as a rejection of food. Given that the child is wasting from the vomiting, It certainly does sound as though it is much more than your spit-up sort of vomit.

Is there diareah or constipation, dehydration, lathargy, body temp issues, seizures, etc?

BTW - have they tried an elimination diet?