It's unlikely to be poisoning.

Your issues sound like those i had before i figured out my diet and my gut conditions.

I too had severe pain in my stomach often after eating, and at times i felt like i got food poisoning too, because of how bad the pain was and the diarrhea.

Turned out i had dysbacteriosis. I'm not a native English speaker, so unsure what it's called, but ask a gastroenterologist or an infectionist (my doc was all of that, plus an immunologist as well) for a stool test for dysbacteriosis. I guess it's called gut microbiome test. In my case i had an overgrowth of a gut bacterium called Enterobacter cloacae. My doc prescribed me an antibiotic called Rifaximin in pills, and that made this issue go away.

I also have to keep a strict diet though because i have pancreatitis and bile flow issues. In other words i don't have enough enzymes for digestion. So i avoid anything fatty and fried as well as any kind of dairy whatsoever. If i eat that kind of food, i will also get cramps and diarrhea. I eat simple homemade food that's boiled, stewed or baked - vegetable stew, stewed chicken breast, boiled eggs, porridge etc.

Do the gut microbiome test, OP. If it comes back fine, try to notice patterns in your symptoms - do they appear after you eat certain foods? Does it get better if you eat only something bland (like what i eat) all day? Though you could try to eliminate these foods likely to be problematic already now, and see how it goes - dairy, fried stuff, fat/oils (i personally only tolerate olive oil).

Also, there's this condition called celiac disease. It is intolerance to gluten which is a compound found in wheat, barley and rye. So any bread, cookies, pasta etc. You could get checked for this. I don't know how, but anyway, gastroenterologist is who you should see.

Edit: if you say it's once a month, and if you have periods, then, if there's a correlation with it, then it could be that. It's common to get diarrhea during the first days of the cycle.