I had a vasectomy 35 years ago. During those years I have had relationships with three women, none of which got pregnant for the obvious reason. But with this last relationship, her period is late by about 3 days. My vasectomy was done the traditional way with scalpel , a section removed, folded, stitched, and cauterized. What are the chances of a vasectomy failure with this procedure after 35 years?