I tell you what I would do.
First:
You call in sick tommorow morning, migraine, whatever, take a few days off, paid and take pleasure those fuckers are paying for you to sleep in and take stock.
Second, you contact your GP tommorow and tell them everything you have said here and that you need support for your mental health , I'm hoping they should arrange for you to refer to speak to someone. That's what I did in a particluarly bad job where I was exactly in your space.
Thirdly, you will begin a campaign to get a new job. I work in the City and at one bank, I would cry myself to sleep each night, and in the bathrooms at work. I was racially bullied in such a subtle, sly way, even keeping a diary of the abuse read back as easily dismissed - people stopping talking when I approached , not being invited to social events, criticism for every project and work I was involved in, ignored in meetings and literally raising ideas, ignored, then one of the gang raising the exact idea and the boss showering them with praise.
IT was toxic and left me in therapy, I had many jobs in similiar firms before this shit job, life long friends who I even went on holiday abroad with, it was just this toxic job was a perfect storm of a bunch of racists all in the same place at the same time. After I left , I had a great team again.
Searching for a new job will help see light at the end of the tunnel, getting professional help with help with your mental health. Dis-engage with the place, surf for jobs every lunch time and do just enough to keep the job until you get the fuck out with another job.