Hi, thanks for asking in Healthcare Magic. Most often, UTI is caused by gram negative organisms. Acute infections usually involve a single organism and are self limiting.. Recurrent or chronic infections may be mixed infections. It could be due to many reasons like bacterial infections, Diabetes Mellitus renal calculi (stones) etc. Since you seem to be getting repeated infections, cause of UTI needs to be investigated instead of taking antibiotics every time. Bacteriological investigations are important in deciding the choice of the antibiotic. Although we dont usually wait till the arrival of report for starting the antibiotic, urine sample must be collected before starting the therapy for better results. Most antibiotics attain high concentrations in urine and so may be effective in lower UTI. But in upper UTI (like pyelonephritis), the antibiotics needs to be concentrated in kidney tissue. Antibiotics are given for 3 to 5 days. In recurrent UTI, the choice of antibiotics are Cotrimoxazole, Cephalexin or Norfloxacin. The pain you are experiencing may be due to cystitis (bladder infection), pyelonephritis (kidney infection) or renal calculi (stones causing obstruction and subsequent infection). Ruling out these possibilities is necessary to decide further course of therapy. Inadequate therapy or indiscriminate use of antibiotics is often harmful as it can result in development of resistance. The organism or bacteria will not be sensitive to the antibiotic if it becomes resistant to it. Hence you should complete a full course of antibiotic. I hope it is useful to you.