I Developed Diarrhea Wednesday Morning. Since Thursday Morning I Have

I developed diarrhea Wednesday morning. Since Thursday morning I have had bright yellow watery diarrhea. I have followed a clear liquid diet and a BRAT diet but within min or an hour I am having more diarrhea. I don’t have a fever. I have had a slight headache and have been tired. I am producing plenty of clear urine so I’m not dehydrated. My stomach doesn’t hurt unless I need to have a bm. I went to urgent care and they sent me home with a stool sample kit but that was it. I don’t have a gallbladder. What could this be?