Found myself in a similar position OP. I worked my bum off to get from being a single mum on benefits, having given up a very good career due to my situation, to earning a decent wage doing a job that I hated.
I looked into all sorts of other careers, different options and spent 6 months jobhunting. All the while going from strength to strength in the job I hated (I was really good at it, but it was ridiculously stressful).
I ended up having a breakdown, signed off work for 6 months with severe depression and eventually being dismissed on health grounds. I think it is important to try and get yourself out of a bad situation before it gets to you the way it got to me. I had other factors that influenced my illness, the main one was the job though.
Fast forward 6 months, I'm now working part-time Mon-Thurs, 16 hours in an office and I love it. I love that I'm not in charge, there's little stress and I can run my personal life/cope with stress/deal with my illness AND work. Ideally it shouldn't have come to this, I should be working full time but that is beyond me at the moment - I hope that this time next year I will be looking at increasing my hours, hopefully my MH issues will be sorted (hopefully, who knows!?)
So, my point - do something now, before your hand is forced.
Good luck 