Is confession valid if the penitent doesn’t remember how many times he committed a mortal sin?
The Baltimore Catechism:
Q. 792. What should we do if we cannot remember the number of our sins?
A. If we cannot remember the number of our sins, we should tell the number as nearly as possible, and say how often we may have sinned in a day, a week, or a month, and how long the habit or practice has lasted.