I get sick every year for some reason, often gastro, and the bi-yearly AC switch off/on giving me a long cold because I grew up in a country without AC. A year

I get sick every year for some reason, often gastro, and the bi-yearly AC switch off/on giving me a long cold because I grew up in a country without AC. A year out of two I have a bad flu, a year out of 5, a bad otitis so painful I can't eat for a while... Well the ONLY year of my life (I'm 33) I wasn't sick was 2020-2021. I think... the mask helped a lot. I feel like I understand now all these people telling me getting so sick every year wasn't normal...