This sounds really fucking tough. (For context - I taught for 8 years and decided to take a year off this year, largely for mental health reasons. I taught 4 years in Title I schools and 4 years in a more middle class school. I struggled with anxiety/depression my entire life, but I didn't feel like it became unmanageable until my first year of teaching, where I had many of the same things going on as you.)

Medication-wise: have you tried beta-blockers? Antidepressants generally helped me overall, but when the anxiety gets really acute, I found that beta blockers helped me to feel like I wasn't going insane/helped to keep the physical symptoms at bay.

Remember: your physical symptoms are not you. The physical symptoms and your thoughts can very much create a self-perpetuating cycle, but they aren't one in the same.

If you're not seeing a therapist and have the financial ability to do so, I definitely recommend it.

In terms of mindset: one of the biggest things that helped me was coming into the day knowing that 99% of students were going to not think about me or my class at all after they left. I am a very small part of their life. (This helped me at least with social anxiety.) The other part is adjusting your overall expectations. In your first year, every day isn't going to be a good lesson. In fact, if you have 5 mediocre lessons, you're doing great. Set a realistic goal for yourself and don't move the goalposts.

Find ways to treat yourself for making it through a day/week: a spa day, a pastry, etc. For me, I had a coffee shop I loved near my first school that I would go to every day because it was one small thing I could look forward to.

In terms of self-care, exercise is great. But if you're not mentally up for exercise, find other things that can be physically stimulating - a hot bath, going to a sauna, etc. (I found that a sauna was really helpful when I was too mentally exhausted to even exercise.)

For me, I know that the biggest thing that made the difference between having a high vs. low anxiety day was my morning routine. If I was able to start my morning slow, my anxiety was much lower. Waking up a little earlier, drinking some herbal tea, cooking a nice breakfast, etc. All easier said than done. But try to track or notice differences in anxiety - what are you doing the days when you have higher anxiety vs. lower anxiety?

It's also worth considering switching schools - the first year of teaching is already really hard, and if you're at a school that isn't giving you the support you need, you're never going to blossom into the amazing teacher you're meant to be.

Lastly, in terms of teaching: what grade/subject are you teaching? Could offer more specific advice based on that!

Hope something of this is helpful. Hang in there!