You have been on several courses of antibiotic therapy. Testing the urine for infection as well as obtaining a urethral swab for STDs should be done to see if any bacteria continues to be present.
The prostate should also be considered, and examined with a digital rectal exam or transrectal ultrasound. A prostatic abscess can lead to continued infection despite appropriate antibiotic therapy.
If infection has been ruled out, a cystoscopy can be considered to evaluate for anatomical abnormalities (i.e. a urethral stricture or polyp) that can lead to the symptoms.
These options can be discussed with your personal physician or urologist.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.