HI Greetings from Dr.Divakara.P Your symptoms could be due to Urine Infection , Kidney stones or some problems in nerves due to diabetes. Definitely this is not a side effect of Metformin , so continue taking it . For further evaluation for the cause of your problem , I would recommend you to get Urine Routine test, Ultrasound Abdomen Pelvis scan and a per rectal examination done by a doctor. Also let me know if your blood sugars are under control or not . Kindly revert back with the test reports. Any clarifications feel free to ask . Regards.