My experience when overwhelmed is to really stay focused on the moment. I find that when I let my mind go to the future (whether next month or next minute) my anxiety tends to spin out of control. I can usually deal with whatever is happening at that moment, and it is encouraging for me to look back and think "i have made it through 4 hours, so I can probably put a few more together".

I am not a big fan of meds (though I am on some) but there are meds for anxiety and depression that will not make you sloppy with your work. If that is something you want to try, a pdoc might be able to help you.

And, I think acceptance that I am doing something really hard and stressful is helpful for me. It sound like you are not getting much support (for many people learning and holding down a good job is no big deal). But for you, at this time in your life, it is a big deal. I would think anything that you can do to encourage yourself might be helpful.