Someone around here said IBS stands for " I be stumped". Seems bogus to me too.
Non-celiac gluten intolerance (NCGI) can be found in 6 to (over) 10% of the population. It is more common than celiac disease, has all the same symptoms as celiac disease (except the villi damage) and can only be treated with a gluten-free diet... That how you diagnose it too as there are no accepted blood tests at this time although some think the AGA (anti-gliadin antibodies) tests may show gluten intolerance in those with NCGI as well.
Two of my three kids had symptoms like yours but they also tested negative. I am a celiac so I chose to not trust the tests and made our house gluten-free - they are doing much better now. It could be NCGI or it could be celiac disease but it really makes no difference in how one treats the diseases. It's just a label.