I had a friend who had a very simmilar condition to the one your describing, after he ate not to long after he would vomit and he could barely keep anything down. the only way he could keep any food down was to eat very small ammounts & this went on for years. He saw a bunch of doctors all who said ether there is nothing wrong or its all in your head but he was persistant and finaly one doctor took an interest and they found out that it was a condition that caused his esophagus to narrow & spasm which caused him to vomit. so to make a long story short he required surgery to fix the problem, but since the surgery he has not had a problem and is able to keep food down. Im not sure if this helps you but I figured id post something cause the condition sounded so familiar anyway hope this helps you.