There are many causes of blood in urine like kidney
stones, infection of the urinary system, kidney disease
, blood clotting disorders, medications like aspirin,warfarin,phenytoin,quinine,antibiotics ,chronic diseases like diabetes,hypertension,viral infections etc.Only blood in urine without the presence of leucocytes or pus cells may not always indicate urinary tract infection. Taking aspirin for such a long time can cause blood in urine. It is best that you discuss your case with a urologist.