Yeah I get that, and I feel the pressure massively too! A lot of the procrastination advice out there is sort of cliche, and you might turn your nose up at it a little, but my advice would be to try a bunch of different things to find what works for you. I'll write what works for me:
For starters, removing distractions. I remove my phone from the room, and don't really have any socials that I use on my laptop. Make sure you've got a nice place to work (clean, has everything you need to study) and make a list of what you need to do/what you're going to revise.
You can make a revision timetable, personally I find those more stressful if I don't follow them, but that's something to try.
From your list of tasks, pick 1 thing that you can achieve that day (do more if you have the time- better to do more than you expect than less). Break that task down as much as you can, if it's a subject, pick a topic to do first, if it's a studied text, focus on the characters or themes.
Then work out how you're going to approach it- is it learning the content stage, or doing a past paper stage? If it's science content, then watching a FreeScienceLesson video is a perfect thing to write down.
I find that this works for me because I love ticking the things off (all about seeing yourself be productive!) and so having a list of lots of little, easily achievable things is nice because then it's a case of 'I'll just do this little thing so I can tick off one more before I have a break' and not 'This is a massive task I may as well not start'.
Also, watching educational videos can be a great way to break the procrastination cycle, because it sort of combines procrastinating with actually doing something useful (and with the grades you're getting you will know a lot of the stuff already, so there'll be lots of times you know you already understand it and hopefully that'll inspire you to develop your knowledge further).
Finally, it is ok to procrastinate a little. We're all guilty of it, and try not to beat yourself up too much about it. Sometimes you have days where the brain is not braining, and that's fine, there's still enough time, and you can always do something simple like put the subtitles of the language you're learning onto a show you're watching if you don't want to be completely unproductive! Try different things, and find what works for you. This is working for me, but it may be completely useless for you! I hope it helps a little though, and good luck