8 weeks of vomiting, nausea, acid reflux, that comes and goes. Sometimes stomach pain during/after.

These symptoms are presented in an otherwise healthy, fit 18 year old young man who has no history of gastic issues. Prior to this, he had vomited twice in his life with a stomach flu virus when he was 1 year old and 13 years old. A grade 3 concussion 2 years ago also produced vomiting immediately following the blow to the head. No issues since. Current symptoms began April 5 - Routine bloodwork, endoscopy, stomach emptying test and ultrasound to examine internal organs have all presented as negative for any specific cause. Doctors are stumped and don't know where to go next. Has lost 15 + pounds. Absences from school due to these symptoms are putting patient at risk for high school graduation.