Counselling can be great for just giving you space to honestly talk about how you’re feeling and to cry if you need to with a non-judgemental other.
Journaling can also be good for just getting stuff out of your head - you can write about the stuff of the day, the situations that are causing the stress or how you’re feeling. Or draw, or write song lyrics that seem to fit how you’re feeling (I found writing lyrics that fit then trying to write a response really helpful).
This will sound a bit “woo” but try writing the facts of what’s happening with your dominant hand, then write about your feelings with your non-dominant hand - it taps into a different part of your brain and can be really interesting.
I don’t find mindfulness at all helpful but doing something your are fully focussed on can give the same headspace. So make a hot drink and really pay attention to how it smells, the heat of the cup in your hands, how it tastes, what you can hear as you sit and drink.
Sensory things help too, so a shower with scented soap, shampoo etc, really nice scented hand cream, a minty or strong sweet to suck. Basically things that help keep you in your body.
If you’re worried about your heart rate speak to your GP about prescribing propranolol, it has no psychological function but will help with physical symptoms of stress like heart rate, shaking hands etc.
With sleep try to rest whenever you can, you may not sleep but just lying down and stopping can help. Slow everything down, keep your days less busy where you can. Try to space out meetings and difficult people so you have time to process what’s happening rather than running from one thing to another.
Stay off work for now, it may not be the cause of the stress but it’s the one thing you can set aside until you feel a bit stronger. I’ve so been there and it was a slow road back, but there is a road back if you give yourself time.