Ive recently had a uti and blood in my urine the doctor described antibiotics. im now experiencing bad pain in my right lower back, buttocks & leg?

Kidney infection?: Urinary tract infections are either simple bladder or complex kidney infections. Maybe your bacteria are resistant to antibiotic so infection spread. Go back to see your GP. Ask for urine culture & sensitivity (American phrase) to identify specific bacteria & appropriate antibiotic. Or pain may be unrelated but still needs to be evaluated.