Don't have an answer but your not alone. My 20 year old daughter has same. Multiple tests and 10k later they just dont know what it us.
MRI of the abdomen w/without contrast and abdominal ultrasound tests may
also help in your diagnosis
Is there any chance of you being pregnant?
If you are sexually active, and even if you are on the change of life (which can take many years) and even if on the pill, you still can get pregnant.
As you have had all the gastric tests done and they have all come back fine, it is likely that you have had a gastric flu bug for a short spell. Did you do the swallow test where you drink a white liquid as they take images? If not, that may be worth getting done. The doctor would refer you for that if you have not had that done.
Have you had your stomach pH tested? Have you tried digestive enzyme supplements and probiotics? Have you done an elimination diet to rule out food intolerances? I found an article from Buzzle with plenty of info...
"Causes of Vomiting after Eating
Common Causes: Inadequate sleep, high blood pressure, excessive exposure to heat, high altitude, motion sickness, sea sickness, indigestion, side effects of certain medicines, exposure to chemical toxins, emotional stress or fear, a reaction to certain smell or odor, fever, overeating, etc. may result in vomiting as soon as you consume food.
Improper Eating Habits: Taking meals too frequently or starvation for a long period, long intervals between two meals, hastily eating and gulping of food, consuming too heavy, fatty meals, eating when not required, eating late at night, may lead to vomiting after meals.
Life-threatening Causes: Dysfunction of any of the body systems may cause vomiting immediately after intake of food. So, you should consult your doctor immediately if you are vomiting again and again and experiencing constant intestinal pain after eating. Blocked intestine, gallbladder diseases, heart attack, brain injury, gluten intolerance, gastroparesis (delayed gastric emptying due to partial paralysis of the stomach), brain tumor, stomach flu, ulcers, meningitis, appendicitis, migraine headaches, dehydration are some of the causes of vomiting.
Food Content: Certain ingredients or certain foods which do not suit your body, are not accepted by the digestive system. If such ingredients are present in your food, you are likely to puke after meals. If you are not used to spicy and hot food, consumption of such food can also cause you to throw up.
Food Poisoning: There are various causes of food poisoning. Bacteria from the contaminated food, improper washing of hands or ingredients, poor hygiene can lead to vomiting.
Food Allergy: Food allergies lead to discomfort, pain, queasy stomach and nausea after eating. Some people have lactose allergy, some have food-color allergy. Some are allergic to gluten.
Side Effect of Therapies: People undergoing chemotherapy or radiation therapy may have to face the problem of vomiting as they consume beverages, snacks or meals during or after the treatment.
Pregnancy: After having tea, coffee or milk in the morning, a pregnant woman often vomits. During the first trimester, she may often throw up after meals. Nausea, known as 'morning sickness' is the main cause of vomiting during pregnancy.
Alcohol: Alcohol abuse often leads to vomiting.
Preventive Measures
Following preventive measures can help avoid frequent vomiting.
Lemonade, fresh or pickled ginger root, cardamom and mint help get rid of nausea. Chewing any of them after consumption of food helps prevent vomiting.
Avoid foods that you are allergic to.
Avoid brushing your teeth, immediately after eating, as it may induce vomiting.
Avoid congested rooms, riding vehicles, too much of exposure to heat as far as possible.
Certain over-the-counter medicines are helpful in avoiding vomiting.
Avoid eating processed food, junk food or food preserved in refrigerator for a long period.
Eat fresh fruits and fresh vegetables, whole grain food as far as possible.
Drink cold or ice-cold drinks.
Do not mix hot and cold foods.
Avoid fried, acidic, greasy, sweet and fatty foods.
Eat smaller and more frequent meals.
Eat slowly, avoid eating late at night.
Drink beverages slowly.
Avoid any stressful activity after eating.
Eat light or bland food if required.
Avoid solid food until vomiting subsides.
Herbal tea, green tea can help prevent vomiting.
Avoid alcohol and tobacco.
Drink adequate water."