It sounds to me like you’re experiencing flashcard overload. I say, contrary to the responses you may get, stick to your method of testing yourself through flashcards and active recall. To get about flashcard overload, look through the topics that you’re not 100% confident on, and go through the cards you made from that topic.
An alternative could be to spend your time doing past papers, marking them and then identifying any weak topics that you have. Focus your time on that, then repeat with another paper.