Procrastination is a coping mechanism, it seems you’re overwhelmed with the amount of work you’ve got to do with revision. The key thing is to break it all down into manageable pieces and start small (I can’t stress enough how important this is). Spend some time thinking about it and really plan your day. Stick to your plan. Pick your least difficult subject and revise for 10 mins and reward yourself with something you enjoy (within reason)and write down what you did (diarise). Then increase to 15 mins when you’re ready. Find the way to revise that is enjoyable at least in some way (e.g. try revising with a friend, watch a video on the subject, make flash cards). Once you get going, you will realise that you enjoy making progress and achieving results and the rest will follow.