I'm an O neg being very careful, and I've noticed that as I've gone through my months on the diet, new food sensitivities have popped up at certain intervals. First it was soy, then glutens, then grains. I was okay on rice for a while, then not, okay on beans, then not, okay on apples, then not...etc.
For me, the trigger and alarm is my sleep patterns. When foods are wrong, I sleep heavier, snore, have bladder trouble, and wake with nasty pain in my ribs or low back. So, I nix the possible offenders for that day and the next, and check how I feel in the mornings. That's how I figured out each offending food. Then, if I'm in a cocky mood, I add the food back in and see what my symptoms are. But, I don't do that too often!
We each have an area that is our trigger, or our reactive spot. For you, it's clearly this GI thing. Instead of cursing your sensitivity and reactivity, use them as diagnostic tools. Your body is yelling, "Hey! Something's very wrong here!" Just listen.
Your living situation sounds very stressful, which can, all by itself, trigger the heck out of a GI tract. And, as it is winter, the mold, fungi, and dust counts in a house--especially one where frying happens--can be astronomically high. Mold and fungi can also trigger--all by themselves--a GI attack.
I know it's scary and infuriating to be taking such mindful care of your health, and then have a big fall-down like this. Know that this can be an immensely instructive transition--if you just sit with and follow the symptoms from inside your own body, and from within your own wisdom. Also know that suffering is discomfort multiplied by resistance.
For many of us O's, the diet we end up with is a paleolithic diet. Just meat, veggies, nuts, and small amounts of fruit. Boring, boring, boring! But much more boring is to wake up in awful pain from grains or beans, or be doubled over from whatever! Perhaps going paleo for a few days will help to calm down your symptoms? Now I'll shut up!