Some people may object to this suggestion but it saved me in a similar position to OP'S.

I was working in a well-known hotel on minimum wage, 50+ hours a week. There was a change in management and a lot of staff walked out; suddenly we were incredibly understaffed and it took a huge toll on my mental and physical health.

I walked out and went on Jobseekers Allowance. Initially they told me you can't claim if you actively quit your job but I almost broke down in tears in the office and pleaded with them why I had to leave.

I got my claim and it gave me a chance to get myself back together and find a new job. Can't guarantee they'll listen to you like they did with me but it's possible, and it really saved me at the time.

Hope you'll be ok.