My 17 Year Old Son, Has Had Occasions Of Vomiting

My 17 year old son, has had occasions of vomiting after he eats, he has found it to get better if he eats slower and avoids spicy foods, also he is experiencing mild to moderate fatigue, he told me he is sleeping well at night but still feels tired during the day. Over the last 2 weeks he has also felt mildly ill. The vomiting has been going on for a couple months, off and on. He may go 2 weeks without vomiting. He is an athlete otherwise healthy.