I have been a chronic sufferer for many years and there were a variety of causes. Underlying it all was gluten sensitivity as I had both Celiac Disease and Leaky Gut. Going gluten free 5 years ago did not stop the problems tho I did feel better. A big problem is that the usual blood tests and endoscopy biopsies are false negatives about 30% of the time. A new study has shown (see Celiac.com newsletter) that people with symptoms but negative tests are metabolically the same as people with positive tests. They advised people with negative tests to stay strictly gluten free.
I did Hulda Clark 's programs for years and after I went gf they worked much better and I got out many parasites from the small intestine and bile system using various parasite herbs followed by Liver Flushes. For Tapeworms I used 3 to 5 weeks of Quassia altho Clark advised Coenzyme Q. I also used a Clark's Zapper. However I still had intestinal problems - yeasts and bacterial overgrowths and then because of another problem had a Vit B12 blood test which showed a large deficiency. Since taking B12 my intestinal and other problems are much better. I found a pure B12 online so am avoiding the chemicals and aluminum in the pills and injectables (also taking Betaine HCl). According to a new study about B12 levels a person can have a deficiency for some time before showing larger than normal size red blood cells and often Drs only look at the size of the rbcs as a sign of B12 deficiency.