Sometimes I will go months with no stomach issues then for no reason I start getting upset stomach. The only thing I can come up with is that when my sinuses act up and I get a lot of post-nasal drip, then my stomach acts up. This year as soon as the rainy season started, I began getting stomach aches. It may be due to mold growth in my house because of the high humidity. I know that houses these days are built more tightly and have less ventilation which leads to mold growth in humid conditions. That little fact right there will cause a person's sinuses to act up which in turn causes stomach aches.