It's time for you to take a couple of steps back and breathe for a few moments.
If you don't relax a little, you stand a good chance of either making yourself sick with stress or making mistakes that are a result of being wound too tight.
Get yourself a small notebook and start writing in it daily. Write questions that occur to you that you don't have time to research on the spot. Write little tips and tricks that you learn from your coworkers. Write near misses that you don't want to trip you up in the future. Most important, write things you did well, problems you solved, complements you received, and and all successes that come your way.
When you are feeling overwhelmed and depressed, pull out that little book and look at the progress you've made.
What you're suffering now is two things--a serious, though understandable, lack of perspective and a self-centered outlook borne of fear.
Your perspective is too limited right now. You are so focused on the two inches in front of you that you can't see the big picture that will help you let some of the tension go. That's normal, but it's also painful. Keep telling yourself that you have made it this far, you want to do a good job, and you will keep learning. Follow the policies and procedures to the best of your ability--they're designed to help you avoid mistakes--but understand that no one is perfect. You will make errors now and then or forget something or misinterpret something. But if you develop good habits, hopefully, your mistakes will be small ones or you'll catch them before anything serious happens.
The self-centered outlook is also normal. Anxiety tends to narrow your focus. But it also increases the chances that you'll miss things. Again, step back and try to look at the big picture.
In the not too distant future, you will find yourself feeling better and actually enjoying coming to work. Don't be afraid to ask questions. "Off orientation" doesn't mean "knows everything now," and no one expects that of you.
Take good care of yourself physically and shift your attention to something completely different during your off hours. Ride a bike, watch a mindless movie, bake bread, get or give a massage. Let your poor ol' brain unclench and everyone will benefit.
I hope this helps.