I want to get some more detail information about your problem-
How long the problem is there?
Which medicine for the blood pressure do you take?
Have you done recently echocardiography? ECG?
Do you have any other disease?
Do you take any other medicine?
Waiting for your reply.
Thank you for the information.
As kidney function is normal according to the test done by your doctor, there may be problem with your heart.
You need to do repeat urine analysis, Complete blood count, blood urea, creatinine, protein etc. Echocardiography, ECG to find out the cause of edema.
As the problem has started with lower back pain there may be some other pathology in the kidney or in the spine.
Detailed examination and investigations are needed to come to a conclusion.
You should contact your doctor as early as possible.