considering you are 64, your chances of getting an erection, maintaining an erection, getting aroused, is much lower than people that are much younger. its caused by the meds.
if Viagra does not help then you have probably suffering from valve issues.
your erection is effected by the meds you are taking and I am sure the Dr. you are seeing has told you these facts.. BP issues destroy the valves that hold the blood in the penis for the erection to hold.. You need to see an urologist that will exam you for the best fix.. I would say after 8 years it is time to take some action..
I suggest some exercises. Google these words and research on sexual health.
Male deer exercise.Female deer exercise for your partner
microcosmic orbit
kegel exercise.
Abdominal breathing.
Yoga energy locks.
Visit web sites of yoga and taoist yoga and Zen.You will find some technique suitable to you. wish you best of luck.