7dpo bad diarrhea?

Help! I woke up with a stomach ache feeling nauseous. Now I have liquid poop... literally running like water. I have been cramping really deeply since 4dpo. Is this a symptom. I ate the same thing everyone else ate... why am I the only one really sick? I was avoiding throwing up and now I have diarrhea. So bad to the point I can't stop it once it comes.