Hello, I recently was given a 7 day course of amoxicillin for a sinus infection. I came back to the hospital because the sinus infection persisted, and I was given azithromycin and codeine/APAP. I was taking 600 mg ibuprofen twice a day during the 7 day course. After taking azithromycin and the codeine, my stomach went into an instant gnawing pain. I went back to the hospital and I i was told to take prevacid. Now I m defecating yellow soft stool and I have a throbbing in my gut that can be felt in my lower back throughout the day. What is going on?