hi there, looks like you have a mass lesion or retained urine or any such pathology in your bladder which is giving rise to the black shadow, though the radiologist
will be able to give you a better report after looking at the film. The blood in urine is a possiblity considering this situation and it could be microscopic quantities such that you are not able to appretiate its presence in urine by naked eyes. If this has been going on for the last 3 months then I strongly advise you to visit a urologist
and get yourself thoroughly checked. It is not to be neglected and sooner evaluated sooner treatment can be started.There is a definite pathology which needs to be treated. Take care.