Right side back pain

Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the right sided pain in the back(loin) for the past 2 months with lethargy and increased frequency of micturition.
You might be suffering from renal calculi. Loin pain commonly originates from the kidney. Renal calculi are common and cause severe pain. However other sources of pain need to be considered such as pyelonephritis, abdominal aortic aneurysm, musculoskeletal pain leading to spasm.
You must consult your urologist who may like to conduct complete urine examination to look for pus cells and microscopic haematuria and ultrasound KUB that will help in diagnosis and further management. CT may also be required for the diagnosis of renal stones.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.