You don't have to answer this OP but I'm guessing you teach English. If so I totally understand the amount of marking. It can take me 30 minutes to mark a piece of extended writing, so a class of books can take me most of a Sunday. It is ridiculous.
I also appreciate how hard it is not having your own classroom and base. Constantly moving around, in a room that isn't set out as you like, having to cart books etc around.
Our school is on a huge site, our PT teachers don't have their own classrooms. I understand how difficult this is.
I nearly lost my nerve when I had to cover a bottom set year 10 class a couple of weeks ago, The behaviour was appalling, I coped, held it together, managed to get them settled, but inside I was shaking, thinking "I can't do this." It was the last period, and I went home and howled like a baby.
I think most teachers, at some time, have felt this.
I'm a single mum, I can't afford to get out. I also do private tuition, and it's much more satisfying, because the students want to learn.
If I was you, I would get out, and do private tuition whilst you consider your options and possible career switch.
Long time stress related illness is a concern at our school. I have seen brilliant, dedicated teachers buckle under the pressure, it's a real shame.
Mostly I enjoy my job, but I no longer love it. If I could afford to, I'd get out. I totally understand and empathise with you.