I afraid I can’t really help, I’ve been going through the same thing.
IBS, unbelievable constant farting, tiredness, etc etc.
I cut out dairy, it helped for a bit, then it came back. Now I can’t touch anything dairy or I’m in a right state, I used to be able to eat ice cream and be a bit rough, now a mouthful of it and I’m in bits.
I cut out red meat, helped for a bit, steaks give me really back stomach aches, but it’s come back.
Dr. says it’s most likely stress and, whilst didn’t quite say the words “quackery” it seemed their medical opinion that a simple hair / blood sample isn’t enough to tell you about ‘intolerances’ and in fact, apart from certain conditions like Coeliac disease and Crohn’s food ‘intolerances’ are mostly a myth.