If you don't see any patterns in your data, yet day-to-day fluctuations persist, he is reacting to something you aren't tracking. Look elsewhere.
John was doing terrible in school again. His teachers were at wits end. I looked through three years of data, but couldn't see any patterns, none at all. What was causing his adhd? What was the mechanism?
After several controlled experiments I finally realized that his pure, whole grain bread brings on a huge reaction, while a white refined bread, loaded with preservatives, calms him down. Obviously gluten is not the issue. What does this mean? What does whole grain bread have that white bread does not? What is in wheat germ/bran that is not in wheat starch?
One significant difference is lectins, a set of biologically active proteins that are prevalent in the husks and skins of most plants. I read <the lectin story>, and put John on a lectin-free diet. This helped for a while. (It seems like every change helps for a while, or else we are desperately searching for improvement.) But it didn't last. Soon his behaviors were as bad as ever, so we gave up on that theory. But it was a good try; we'd never tracked lectins before.
Here's something else we never tracked: whether he ate his salad first or last, whether he ate that apple on an empty stomach, whether he went to bed immediately after dinner, how much oil/fat was in the potato chips, etc. All these factors are important in the ibs diet.
Yet why should the ibs diet help someone with adhd, someone who has no overt digestive disorders? I had no clue, but we had to give this diet a try. (It didn't help for long.)
I'm going to describe two forms of IBS, A and B, with the understanding that Wendy does not fit completely into either camp. Type A is intrinsic. Your intestines have normal flora, but they react to things, oils mostly, and insoluble fiber, and seeds, and other things. See <Eating For IBS> for more details. Type B is a bacterial imbalance. It can happen to anyone. It goes along with the high carb diet that we all eat here inthe the United States. When the bacteria get out of whack, they can cause any symptom in any person. My wife has explosive diarrhea, and my son goes insane. You never know what the mutated bugs are going to do to you.
So how did my wife fit into all this? I thought I understood Wendy's symptomology in 1995, shortly after her symptoms got so much worse, but I have since refined my theory. Yes, she has some of type A. Oils are real bad, but only vegetable oils. Dairy is ok. That's not typical, dairy is suppose to be bad for these folks. And insoluable fiber actually helps her, whereas it should cause trouble. So she's partly type A.
After a few years of really poor eating habits, lots of carbs, she developed type B. She would react to anything, any meal, didn't matter what. I couldn't see type A at all, because type B was in the way. It took a long long time to figure it out. She finally backed way off on the carbs, and had 5 grams of fiber with each meal; and over a few months her bacteria returned to normal. Type B was cured. But she will always have to be careful of her overlap with type A. Very little vegetable oil, and not too much sugar, and no meat that is more than one day in the fridge.
Bloating is often an indication of type B. Bacteria ferment your food and produce gas. But there are no absolutes in this game. I can only give you some ideas and pointers, things that apply to others, and things that apply to my wife; you will have to play detective and figure out how you work, along with your doctor of course.