Would you like to say some more about what's stressful about your job? Maybe there is something that can be done to ease this.
Do you have a diagnosis of depression that is ongoing/recurring? If your company is of a certain size, they are legally obligated to support you in making adjustments to accommodate your mental health needs.
You might find this helpful, its an article by Mind on Surviving Working Life.
Mind guide to surviving working life [link] Both I and my manager find it really helpful.
I used to self harm in the loos at work. So I can relate to some of what you are going through.