Thanks for your query.
Noted history and understood the concerns.
35 years is a long time to suffer from blood n urine and since you are 71 years old now and are getting blood in urine after bowel movements it is of utmost importance to get a proper evaluation in the following ways:
Consult an Urologist
Ask for MRI angiography
of the pelvis area to see for any aneurysm
, A-V Malformation.
Urethrocystoscopy to see for possible cause of bleeding.
Per-rectal digital examination.
All these things will lead to a proper diagnosis.
Some of the investigations may need doing again and again as the bleeding is occasional and the lesion may be found out only on multiple examinations.
The treatment will obviously depend upon the cause thus found.