What are ways I can tell if something is not GF?

I've been getting sick, and idk what has been causing it. I tried using Google, but something is not correct. Or maybe I need a whole new kitchen at this point. I cook for my family, mostly so I can cook for myself and be in control of what goes on my plate, but I'm the only one gluten free. My partner can't be gluten free because she has arfid, and she's already restricted enough, and our roommate just doesn't want to. And I mean, if they don't have too they shouldn't. But I feel like even the air is not safe (it's a small apartment) oops this kinda turned into a rant/vent.

Idk what's going on, I thought I've been safe with my GF alternatives, and I've been getting stuff that SHOULD be naturally be GF, but maybe I didn't look hard enough or something. I feel like I'm going crazy.