Hi Nick,
Maybe quitting the job is not the best decision at this time.
I can say that you're in the "burn out" stage.Burn out does not only affects your job performances but also social and personal commitments, reduces creativity and innovations and most specially affects one's physiological and psychological state...which means leads to a number of diseases.
Before burn out ruins your life, you have to empower yourself to overcome this thing.And one of the best way is using stress management activities and exercises. Try it, I know will help you a lot.
And when things worked out...that's the time to think if you needed to change your job or not. A relaxed mind will give you more perspective
Aylah