Do you have anything you take for anxiety/stress? Anyway they sound reasonable options with the class, you might do better thinking about them if you can get some sleep. Oh I'm sounding really pathetic here, probably no help at all. I know what you mean about letting people down, I hate that too. I'm a teacher and have been off sick for 8 weeks, and the kids have only had a cover supervisor with them most of this school year. I feel really bad about that. But there comes a time when your health has to come first, so try not to feel guilty, it's not your fault.