I Felt So Terrible I Thought I Had A Kidney

I felt so terrible I thought I had a kidney infection but my doctor said it was only a UTI and gave me (common brand names bactrim, septra) bactrim DS and sent me on my way. This was Wednesday.
It's now Sunday and I'm stuck in bed with terrible lower back pain and right side pain my head is throbbing and I can barely get out of bed. It's been like this every day since Wednesday, is it a kidney infection and the meds aren't helping?
I'm extremely lethargic and dizzy, I feel weak and I keep getting confused and forgetting things.
Should I go back to the doctor?