You need to heal, treacle and it sounds like you need time and space to do that. I'm guessing that you are juggling grief, with teacher guilt. You don't want to let anyone down, with sports day and your class for example, but you need to grieve too.
Get some paper, and make a two column list: Treacle's needs vs. Job needs
List what you want to be able to do, in an ideal world, right now if you weren't at work.
In the job needs, write down what needs to be done at work, essentially.
Now look at solutions. How can your job needs be fixed and where you will get the opportunities to fulfil your needs.
Then, use the job needs column to have a chat with your Head. Going to her with your potential worries, and with solutions, should get some results (if your Head is decent)
Use the treacle needs column to start giving you some tlc. Small steps, sweetie. Please don't get overwhlemed no matter how all encompassing it gets. Xxxx