When to start hard core revision depends on the person and how they fell they are coping in their subject.
I personally feel that making notes and flash cards at the beginning of the year prepare you for hardcore revision because they will make your revision so much easier and by then(after reading notes/flashcards) you could move on to past papers.
Unfortunately, it is a bit late for flash cards(lol why did i bring that up)
Anyway, you are not alone, literally everyone, well the majority are in thye same boat as you.
All in all, you should be focusing on past papers now.