My Now 15 Year Old Son Has Been Experiencing Vomiting

My now 15 year old son has been experiencing vomiting along with dizziness for several years now always having a growth spurt from half an inch to 3 inches. We have been to doctors (family and WE) along with specialists (ENT and pediatric neurologist) to find no answers but also nothing he can do and it usually lasts 3-4 says when occurs. We have heard everything from vertigo and meningitis then they all off the table but no answers. Neurologist and ENT found no issues. I would just like to not see my son go through this if related to puberty and growth spurts I understand but he missing school when this hits and would like to not feel this way. Seriously frustrated....Brittany