I'm not surprised to hear that you hava a history of Antibiotic use which is almost always the cause for overgrowths of opportunistic harmful gut microbes. Antibiotics don't selectively kill only the bad bacteria, they kill both good and bad bacteria. Then your digestive system repopulates with the remaining dominant bacteria. So the ecosystem is changed, and it's generally not for the better.
Once the harmful bacteria start to dominate, the immune system of the host becomes compromised. That's where the mold and chemical sensitivities come from. When I was at my worst, perfume would make me feel sick, nevermind mold and mildew.
The "good" bacteria in our GI tract are our first line of defense and are critical to proper digestion and the absorption of nutrients.