What could cause both my mother and me to have nausea, dizziness, chills, and headaches?

Diarrhea is caused by a virus . Sounds like a stomach virus or flu. Drink Gatorade to replenish the electrolytes you are loosing every time you go to the bathroom so you don't dehydrate. Try the BRAT diet ( Bananas, Rice ,Apples & Tea) its great for stopping diarrhea naturally without any meds. You might want to stick with drinking only out of 1 personal gl so as not to spread the germs back and forth. Hope you both feel better soon.