Talk to Gastroenterologist on Not Sure But A Gastric Problem

Okay, I don't know what is the problem with me, but whenever I eat something and I just cannot bear the food in me, and I just vomit it out immediately, like just after five minutes, two minutes after eating the food, or even sometimes during eating the food, it is not overeating. Even if I eat a small amount of food, I just vomit it by myself rapidly, and you can tell me the cause why I am doing this. I just feel like I am full and I am overeating, but in real, I am not overeating. It is not something like that. Can you tell me what is going on with me?