Hi!!! Congrats on your AC, that's absolutely brilliant!
What are the timelines for the AC versus university work? I'd start by taking a look at that so you can ensure you are prioritising the most pressing issues.
And make a timetable that is doable but incorporates lots of time off, as well as lots of exercise and some socialising. And lots and lots of sleep. Eating well and taking time to do things that genuinely chill you out are just as important as doing work. Having a timetable means that when you are not in work mode you can tell yourself that you should not feel any guilt about taking time out. What really really chills you out? For me it's a bubble bath, sitting in a park with a coffee, or spending time with animals. So I make sure I do these when studying!
What I found really helpful for AC prep was to put everything together into one folder like a little cram bible, with a tick list at the start of everything that needed covering. Seeing it in front of you physically helps show how much work you've put in and reassures you that you HAVE done everything you can!
A helpful thing with uni studying and with AC prep is to remember that it's helpful to learn something, put it down and return to it when you're forgotten it a little--it helps ensure you REALLY learn it. So actually dropping uni work for a little bit to focus on the AC, then going back, and repeating is not a bad thing.
Make sure you take some time to chat with family/friends to de-stress, both for it's own sake but to also keep things in perspective--I can guarantee you that when you feel you haven't done enough, you've actually done 10 times as much as you imagine. In my experience most future lawyers have ridiculously high standards for themselves, you are almost certainly being too hard on yourself.
Another thing that helps with feeling overwhelmed from study is to mix up the study modes--flashcards, saying things aloud, testing yourself, making slides--try mixing things up so you're not just curled up over your books getting worse and worse back pain! Anything you can do on the move is great, I love reading and walking (as long as I avoid roads...) especially if I have a small book or flashcards.
Burnout is horrible and the only way to deal with it is a genuine rest. Depending on timelines that might not be possible right now, but look at your calendar and figure out when you can do 3 days of just absolutely nothing. And pencil that in!!!