What Causes Abdominal Cramps And Diarrhea?

Having severe cramping & diarrhea off & on for about 10 hours. Thot it was constipation which I struggle with so used saline enema. Hadn’t had much of BM since last Sunday when I had same thing Had eaten a few oysters on Sat. I’m allergic to shrimp. Ok all week till this morning. Took 1/2 Imodium at 7:15. PM Still cramping & having diarrhea about every 30-45 minutes. I’m gluten free & had colonoscopy about 5 years ago & endoscopy about 3 years ago. Had yeast in esophagus. I’ve had acid reflux for about 18 years.but stopped PP I after I lost height & went gluten 2 years ago. I use Zantac occasionally. I’m 70. I took Zofran earlier as my usual problem with acid is nausea.