Hi ak, well you've already got some really good feedback............so not a lot to say..............but it does sound like your job can be stressful/pressurized and under that type of condition anyone can potentially make a mistake/s, but with the way you're feeling on top of that as well..................
So, yes, you still have a functioning brain, it's just getting a bit much thrown it's way right now to handle it all as efficiently as you may like. Our brains can only handle/take in so much, right?!!
Do you think you could pull in any techniques to help you a bit more at work e.g. preplan/write down what you need to get done (that way maybe you'd have seen just how big a job you were about to take on???) and prioritize, identify when someone else can help and with what, set some deadlines to meet, try to find some easier/quicker ways to do some things, ask other people how they're managing to get things done (if they are!!!) ..................And if you can take a few more (breaks) to allow you to "release some of that tension/pressure".
It is really good that you've made an effort to seek out help for what's going on for you though, and that you're trying to make some changes you feel will benefit you.
Best wishes
Alison