This might be my simplistic view in life coming into play right now, but take a nap, blank out, whatever. Rest your body (and brain!!) before everything else. It makes everything a lot easier. Set a timer for a nap if you need to. I once took a nap in Geo and my teacher was pretty understanding when I told him why, and nothing really big came out of it.
For test stress, I’m not really the one to talk, but relax yourself before so that you don’t get frustrated? Take short breaks but if you’re being really unproductive, take a walk outside or something. Also, I find it helps to tell myself to go for another two minutes when I get really productive? Just remember to rest
Don’t forget to drink lots of water (I often forget rip) and I hope everything smoothes out soon
Fighting!