Am I experiencing burnout?

I’m drown in work again. This time I have to grade several writing exercises from multiple classes. I have been doing it since Sunday and now I’m still nowhere near finished. But right now I have been feeling strange. Whenever I’m working I can no longer focus. I get distracted very easily and sometimes even find it hard to keep track of what I’m reading. I have been working much more slowly than I want to, and I have a deadline to hit.

Am I experiencing burnout? What can I do about it?