Hello and thanks for writing in
The symptoms you have explained can be caused either due to infection or obstruction in the urinary track. You have ruled out the infection part. In my opinion you must get your USG KUB or X-ray KUB done to rule out any stone or other obstruction which in causing the problem.
Neurological urinary bladder
can be one of the cause and for this you need to be examined by your Urologist
. So feel free to consult your doctor and follow the advises.
Best Wishes and get well soon.