Some of the reactions from the sensitive stomach must be from the parasites. They usually are able to get things they dont like flushed. But when they are getting many, they just overdo their defense.
I did some experiments with some herbs to get rid of my own parasites. I ate a whole garlic carefully chopped and exposed to air 15 minutes, mixed it with mayo, and got it down. I expected that such a treatment should make the stomach upset as never before, but no. Complete peace and silence. They were stunned.
I did similar operations with dried cloves, as they are easiest to find. Mixed it with foxberry jam. Also silence.
Still its possible that your intolerance against carbs can be relevant and worthy to follow up. I stopped eating carbs for 3 years now, and have never regretted. It took 6 mnds to get over the cravings, but i remember the feeling of joy which radiated from my stomach when it suddenly didnt have to eat more of that crunchy and hard stuff.
So, you might just need some new cooking recipes.