Undiagnosed gastrointestinal issues

[Dbourne]

Been having gastrointestinal issues since I was 13, started off small where certain foods like lactose or gluten would bother me, then about every year I'd gain one new symptom, now 8 years later, I have chronic diarrhea 4-12 times a day, each time for around an hour or longer, nausea, vomiting, bloody diarrhea, pain everyday in left side right underneath the rib that can either be dull and irritating or extremely painful stabbing pain and sometimes go into my lower back,and bloating and cramping after eating small amounts. Every food seems to bother me just depends on the severity. Every about 3 months or so, for no reason that I can find, these symptoms get worse for, can either be a day or up to 2 weeks. I have blood tests, a colonoscopy, and an endoscopy and nothing is showing up except that I am malnourished and dehydrated. These problems have gotten so severe my hair started falling out. I've been put on ibs medication before and a low fod-map diet and neither of them really help. What else can I do to find a diagnosis for my issues? Doctors just usually do those tests and they come up negative, need help, hoping to find advice, difficult to be normal.