11 yr old has had stomach pain and has been throwing up for a month

This is hitting close to home. I came here to find out information on my 12 year old, otherwise perfectly healthy son. He has been throwing up 5-15 times per day for almost 3 months. It's always clear, he is absorbing food. We've taken him to a pediatric GI specialist at Duke, have our 4th appointment today. He's done the gastric emptying can, upper GI, ultrasound on the stomach, x-rays... bloodwork and urine tests out the wazoo. All is clear! And yet it's only getting worse. We took him to an allergist and did discover that he is allergic to all trees, grasses, molds... basically the state of NC. He's getting two allergy shots per week and on allergy medications until those kick in in a few months. IDK what else to do. I get the honor of dropping my straight A student off at school while he bends over in pain and pukes out the window at least once on the 1.4 mile ride to school.
We are all at a breaking point. He has classic soccer tryouts this week, thank goodness his coaches know him and have been awesome about his health issues. Prior to all of this, he had a severe concussion for 9 weeks, the flu, stomach virus and strep for the first time. It's been a very tough road. He's NEVER had an antibiotic before this year, just hasn't needed them.
I am taking him to a homeopathic doctor as soon as the labs for that appointment get back. Just another $400, no big deal... and I can't work full time at this point and haven't been able to for MONTHS because of his health issues.
I don't know why this isn't being taken more seriously. Just because a pill can't be prescribed doesn't mean they shouldn't work faster to find solutions. NO reason for this to linger on for months and months. I find this unacceptable as I write out thousands of dollars of checks to DUKE, WAKE MED... allergists, homeopaths. I feel like NOTHING is being done or taken seriously.
It took me 4 years and 5 doctors and one homeopath to figure out I actually have hashimotos and celiac... THANKS! We are desperate.

Poor guy!
You mention recent concussion, which makes me think of another cause of vomiting- brain abnormality secondary to brain injury.

@lhelbling You mentioned concussion. I am still trying to recover from one myself. I bumped the bridge of my nose on the first of April. I iced it.. went on with life. No broken bone and nothing but a small knot and a greenish bruise. I kept having a nagging headache, I got worse upon rising and I started to tire sooner on walks. I also became more nauseous than usual. It took me 4 week to remember I hit my nose. I still do not remember exactly how I did it. I did go to my family doctor. With his exam he said had a concussion and ordered a ct scan to rule out any sinus or brain damage. I have had to move slowly and not concentrate on anything for long. Just close my eyes sometimes to shut the world out. My point is he may still be having effects from the concussion.. it can last for months not just a few weeks. I am a little past the 6 weeks and can tell it is going to take a month or so morre to recover. I am older, but your son is at an age where he has to do more.. his school work for one. My son had a concussion when he was 16 or so and it was about impossible to keep him from pushing it. School.. work and interacting with friends. Finally threatened to tie him down and finally he was on his way to healing and he had stomach problems too.... long before they had many of the stomach medications they have now. The flu can take a long time to bounce back from.

Instead of the normal barium swallow test you might ask for one that involves food. There are two.. one involves one containing barium which usually is eggs and bacon and in the South maybe grits or toast. The other is swallowing different consistency foods. Just because what he vomits is clear does not mean he is getting the nutrients. I vomit clear mucus and sometimes it just comes up.. not really vomitting... they say it is stomach mucosa.. mucus containing acid. A type of reflux. I have achalasia, Barrett's esophagus and gastroparesis. All which should show in a barium swallow test and or endoscopy or what they call a bravo test..