I’ve had the same problem. I came to a point where I was extremely bloated and had terrible gas every time I ate. The only thing that helped with this was not eating at all: I tried intermittent fasting where I would not eat for 16 hours a day, and only ate during an 8 hour window. At least I woke up and spent the first hours of the day (while fasting) gas free – and what a welcome break that was! However, I do not recommend this as the solution because I don’t think it is a solution. More like a temporary relief. It is not possible, at least for me, to live my life like this. I only did this experiment during four days of my holiday while I was at home and mostly relaxing. Also fasting is not too good if you are already weak or have adrenal problems.
But what I did learn from my experiment was this: obviously every time I eat, for some reason, I end up feeding either fungus or bacteria. Hence the gas as the by product. Now I cannot be sure if I actually have Candida overgrowth; there is the possibility that my bloating and gas are caused by bacterial overgrowth in the small intestine instead (sibo). This would be indicated already by the fact that I get bloated very soon after eating (about 20 minutes afterwards, and I doubt the food would have reached the colon by then?).
Do you know for a fact that you have Candida overgrowth? There is always the possibility that you might have another kind of digestive problem. Especially since you get gas from mostly all of the allowed foods (frustrating, I know as it is the same for me). Weak digestion alone can give gas and bloating, symptoms that are very much alike those caused by Candida.
In any case whether trying to deal with Candida or SIBO, it seems like improving digestion would be important. Are you constipated at all? Or have diarhea? If the first, then it is likely that your digestion is sluggish and transit time slow and the food ends up fermenting in the gut as Raster said. Instead of being broken down and being digested so that your body gets food, it ends up being food for the bacteria or fungus. If you have diarhea it might also mean that you are not properly digesting foods and this can be irritating to the gut as well.
How to improve digestion? Not sure as I am still trying to figure this out myself. And because we are all different you may need to just experiemnt a bit to see what would work for you. Betaine HLC never did anything to me either and now I am just too frustrated to try another supplement. Using Swedish bitters to encourage your body’s own production of digestive enzymes might help. Other than that, raw vegetables can be hard to digest especially if you did not eat a lot of that stuff previously (again, you might not produce enough enzymes for digesting them – swedish bitters might help?). Generally steaming or sauteing vegetables makes them easier to digest. However I did find for myself that if I eat raw veggies alone I have no problem with them. Sometimes the problem can be the combinations of foods in one meal.
Other than that increasing metabolism is very important for improving digestion. I was only able to do that by increasing my carb intake. Then again, I probably do not have Candida overgrowth, as the only foods that I can eat without any gas or bloating problem, are fruits (easily and quickly digested sugars). I also experimented with this during my holiday; three days eating fruits only and all my problems disappeared! Now I am back to work and trying to eat more normal foods and I’m getting gas again. I would not recommend trying something like my fruitartian stint if you know you have Candida and that you react to fruits. That would just not make sense. Still I think the metabolism is an important piece in the puzzle that needs to be considered.