I've been on antibiotics for a uti, but i'm my lower back hurts, nausea, fever, dizzy. should i go back to my doc?

Needs re evaluation: Back pain, fever and nausea in the presence of UTI may indicate something more serious like kidney infection and/or kidney stone. Lack of improvement despite antibiotics is concerning. This requires further evaluation immediately.

Here are some ...: Your described symptoms seem more suggesting some disorders inside the pelvic cavity such as PID. So, see Doc timely to confirm the effectiveness of antibiotic Rx for UTI by examining properly collected urine specimen as well as to go through more detailed Hx, do physicals including pelvic, etc. so to make sure if something else, especially in pelvis, is wrong or not.