Not Keeping Food Down Diarrhea With Intestine Pain. Nausea But

Not keeping food down diarrhea with intestine pain. Nausea but not throwing up. Thought to have c.diff. as all started with sinus infection & 3 rounds anti biotics. Tests came back negative. Most on clear liquid as way less pain. Can have a saltine crackers but tried potatoes in mixer until applesauce thickness... Pain & diarrhea follow. Any 8dea what else to try or what could be issue if not c. Diff. Which I took antibiotics for that & not bettemm