I don't know what exactly was wrong with me yesterday -- whether it was a stomach virus, extremely bad morning sickness, or a foodbourne illness -- but for about half the day I couldn't keep anything down. Later in the day, I improved and felt better, but I never felt entirely good yesterday.
So I mostly slept all day, and then went to bed early last night, and I feel better today. I still don't feel great, but I feel much better than yesterday and I am at work.
For some reason, even when I know I have good reason to be at home sick, I still feel guilty for calling in sick and cancelling my classes. Plus, it makes for more work since I have to re-arrange class material to make up for the missed day, so I have a lot to do today to catch up.
**Update: Interestingly, I got about 4 emails from sick students yesterday who were emailing me to let me know they were ill and couldn't come to class, and I found out that two fellow faculty members were also out ill yesterday, so maybe it was some kind of bug afterall.