I've Had Diarrhea For Several Weeks. It Started After Two

I've had diarrhea for several weeks. It started after two rounds of Levaquin and prednisone for sinus and bronchial issues. I've had stool tests that have returned negative for bacteria or c diff. Today, I am experiencing upper stomach pressure and have no control of when a bm will occur. My stools are very runny and gassy and are also full of mucous. I saw an immunologist today and will be having more testing done, but didn't have the mucous earlier. What could it be a symptom of?