My job is very dirty and labour intensive so i don't understand why I make 1000 words a day on those days, but 200 words a day on weekends.
An object at rest remains at rest, and an object in motion remains in motion
My guess would be on the days you work, your body can stay in a working mode/mindset, whereas when you try to do so on non-work days, you have to force yourself into that mindset, which requires a lot of self control. It also might be your body telling you to take a break, and you're overriding that feeling by writing.
What does your writing mean to you? Can you find a meaningful relationship between what your writing means to you and what your work means to you?
Similarly, what do you weekends mean to you? Can you find a meaningful relationship between what your writing means to you and weekends?
I basically write about slavery and oppression so maybe my job gives me inspiration because it is backbreaking labor.