Thanks for your query,based on the facts that you have posted it appears that you have pain in Rt side of lower back after passing urine .
This could be most likely to be due to presence of a small stone in intramural part of the Rt ureter.
Please consult qualified Urologist
for clinical assessment and get your Ultrasound
scanning done to confirm the diagnosis.
Please take broad spectrum antibiotics like Cefotaxime
along with anti spasmodic like Cyclopam
twice daily along with urine alkaliser.