Sound familiar in my private sector job.

My covering officer was only on paper (usually it was my boss) and there is no one to clear my work when I was on MC or leave -The work just pile up. Like you, I was worried about work when I was sick or on leave. When I was sick, I would come to work in the morning and take MC in the afternoon. The work is so overwhelming that I had to work late and come back on weekends. As such, it is very difficult to take leave as well.

When I sleep, I will dream about work and wake up at around 4am in the morning thinking of impending work. I dread going to work in the morning. The colleagues were very combative and unhelpful. The office politics between departments was severe.

I never know the work is so shitty until I am on the job. Then I discovered that the turnover rate is so high as well.

Finally, I decided that health is more important so I resigned.

My advice to you is leave if the work is affecting your health. Otherwise, endure and endure and keep a look out for other jobs, or try internal transfer.