The not remembering is perhaps the worst part of all this mess for a BS. To ask a question and get "I don't remember" as the answer feels like avoidance. My H was/is a master at compartmentalizing - packing things away in a neat little box in his mind to never be thought of again. It's hard.
Have you done a written timeline? If yes, have you revisited it often to see if things you wrote may trigger more info that your BS needs/wants?
It may be helpful to examine, for yourself, why you don't remember - are you protecting yourself? do you think you are protecting your BS?