I have not raised a grievance but think I might have to.
It's impossible to get into the why's and wherefore's here because there isn't enough information. But if you are not sleeping due to the stress then that is not going to help you at work if what you are complaining about is people being critical of your work. With respect, if things are as bad as you say your work is going to be pedestrian at best and possibly rubbish!
I am going to be honest - there are two sides to every story, and whilst I do not disbelieve you, nor do I have the entire context. But even from a neutral perspective, what have you got to lose by submitting a grievance now?
In a worst case scenario - either you lose the grievance but it is clear that relationships have broken down too far to continue or your management are correct (whatever that means - it doesn't matter right now). Generally the public sector response would be, wherever possible, to redeploy you. Not guaranteed, but they prefer to shift people around rather than deal with it.
Best case scenario - you win your grievance. But relationships will still be broken down and in all likelihood HR will look to redeploy, and it will probably be you that gets redeployed. It's not fair, but it's also what actually happens most often.
Your solution is to go off sick and find a new job - without having one to go to you could be off for some time and that sick leave could adversely impact on getting the job. So my solution might get you a new job, and isn't likely to make things any worse because you are already at your own worst case - having to go off sick and still find a job.
Are you in a union?