What Causes Severe Left-sided Plank Pain And Diarrhea While Treating Kidney Infection?

I am a 30 year old female with history of kidney stones and kidney infections. Approximately 30 days ago I started having left flank pain with urinary symtoms and a fever. I went to the er because it kept getting worse and the doctor admitted me with a severe kidney infection. I stayed 7 days for antibioics, pain meds, etc. When I was released the pain meds helped and once they were out it was apparent they were just masking the symtoms because I was still having the pain (severe) and now with new symtoms- diarhea frequently, unable to eat and/or barely drink anything all day, and when I stand up my vision goes and I feel like I am going to pass out if I dont get on the ground. I am still in severe pain.