Well, tea is your friend. I recommend that you create a bubble (what I do is put on some playlist with the songs that calm me most OR play one song in a loop so I don't even notice what is happening in there. It shuts out the whole world and all can hear is basically whatever I am repeating in my head in order to memorize the subject) and get out every once in a while either to make tea or if you already have tea, just take a sip and let your mind wander off.

Tip no2: Rewrite your notes. Or redraw them in a way that you will remember.
For history, I literally draw mini comics and it really helps memorizing what happens, since it sums up the entire course.
When you rewrite your notes, it'll help put you mentally back in class and it helps remember a lot of things the teacher said during the lectures .
Idk if those tips will help you, though. I hope they will.
*finger hearts* fighting!!

First, Clam down your nerves, Panicking won't solve anything.
Second, Don't stress out, and relax. Just study slowly, but take breaks, you don't want to overdo it.
And lastly, Just make sure you still get a lot of rest and not skipping meals.
Sorry!~ If my advice ..
Wo Ai Ni!~