Hello Thanks for query .Based on the symptoms that your son has think he has pain in lower back associated with frequent urination is mostly due to presence of stone in lower ureter . Please consult qualified Urologist for clinical and digital rectal examination and get following basic tests done to confirm the diagnosis. 1) Urine routine and culture. 2) Ultrasound scanning of abdomen and pelvis. In the mean while give him broad spectrum antibiotics like Cefixime along with urinary antiseptic like Nitrofurantoin andpainkiller like Cyclopalm twice daily and urine alkalizer thrice daily .Later on switch on to appropriate antibiotics as per culture report. Get the prescription of medicines from your family Physician. Ensure he drinks more water .To keep his urine dilute This will help to control dysuria. Further treatment will depend upon result of these tests and final diagnosis. Dr.Patil.