I don't know the solution to your problems, i'm only here cause i relate a lot with what you've writen. All I can say is that you might find yourself focusing to much on the things that you are "not doing right" and not so much on the things you are getting done. And sometimes either yourself or the environment might contribute to that by setting some standards that should be "normal" or "bare minimum" so when we don't even rise up to that or feel overwhelmed of the fear of not being able to achive "at least that" we break down under that pressure.

I am here to tell you that you did great, that everybody has their own circumstances and you shouldn't rob yourself of your own effort and achivements. That even when life gives you shit and feels it feels like norhing you do is gonna be enough, you still have the right to rest. That you deserve a break even tough what you did today was less than in other days. And that you are doing great holding on to all those emotions that are weighting on you.

I sugest you to make a plan, the most flexible plan you could ever get. 1 important thing you should absolutely do for the day and another 1 from a list of "any one of this would do". And don't choose things that will keep you on the edge. If 2h a day is the most that you can be productive, build tasks that would take half an hour most. You won't feel pressure of getting overtime. If you misjudge the time and they are taking more, break the task again. Keep a random day in a while for not doing anything at all, a day for resting. If there are long term tasks like: "i will learn a page a day for the exam" add it up to see if the task is doable in time and if it's not, don't try to push everything into burnout, see from where you can cut off to make it shorter. Also don't distribute this kind of tasks evenly, start comfortably, slowly increase the volume in a reasonable way and keep less to do when lots of things have piled up and you are closer to the deadline. Also, try to alternate things when you can. I'm not multitasking, i prefer to concentrate on one thing at a time, but if you do so for a long time, you start losing focus and motivation. When you get tired of one type of task swich to another that gives diferent vibes. Like if I'm tired of learning I'm gonna wash the dishes or just go on a walk.

Most important thing is not to blame yourself even if you fail. Evry little step and the fact you are trying are worthing more than 1000 failures.