@brown2 - I do personally know how upset you must be.
I have a son, who went through something similar twice and as a result lost of school in 6th and 10th grade.
In 6th grade he developed the extreme fatigue and dizziness/ vertigo. No final diagnosis made. He got better after what seemed like an eternity and could go back to school.
In 10th grade it started with collapsing in school. Total exhaustion probably. He was seen by a Pediatric Neurologist at our University hospital. Many tests done- normal. His gait was that of an old man. She diagnosed him with most likely Fibromyalgia, also because his older sister had been diagnosed with it.
Missed lots of school.
He eventually was referred a Pediatric Rheumatology program for children and young adults to help them manage the effects Fibromyalgia had on them. That really helped, especially learning how to get normal sleep again. With more sleep, symptoms improved.
Regarding your son’s GI issues, was he tested for Celiac disease?
Fibromyalgia often is found together with other autoimmune diseases.