Microvascular ischemic brain disease is a condition in which many tiny strokes accumulate in the deep structures of the brain. These tiny strokes are usually caused by chronic medical conditions like heart disease, diabetes, or uncontrolled high blood pressure. The problem tends to occur in elderly people who have had these conditions for quite a while. Therefore, given the fact that you are a diabetic and that you are 70 years old, the scenario definitely fits.
As the small strokes accumulate, this can lead to impairment in memory and other higher brain functions. When this level of impairment becomes significant, it is called "vascular dementia." The fact that you are having trouble paying bills and remembering important things is definitely a warning sign. I would strongly recommend that you talk with a doctor
about this issue, either your primary care doctor
or your neurologist
Your doctor, in addition to performing a complete physical examination, may want to perform some tests of your mental functioning to determine how severe the impairment is. Some of these tests may be done in the office, but your doctor may also want to refer you for more extensive, formal neuropsychiatric testing. These results will help them decide how best to treat your symptoms.