Multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, stroke, injury and complications of bladder surgery, harm bladder nerves or muscles causing urge incontinence. Diabetes, stones blocking urethra
, tumors etc can also cause this.
Since you also have a brown discharge
and are not sexually active, there might be a bleeding inside as seen in stones and tumors or some injury and even infections.
It is difficult to comment beyond this at this stage.