I consider myself "sick" only when I can't get my head a) off the pillow, or b) out of the toilet.
For work purposes, however, I will call in if I have something I don't want my elderly residents to catch, like a bad chest cold or a stomach bug. Otherwise, I've worked through kidney infections, cellulitis, gallbladder attacks, and (once) even malignant hypertension. A few years ago I was at work when this horrendous headache came on suddenly; when my co-worker took my BP, it was 260/130.
Did I go tell the nursing supervisor and check myself into the ER? Of course not: I waited until the next day to go to the doctor, and by then the BP was down to 180/110.
It was totally stupid; I could've stroked out right there on the floor even if I WAS only in my early 40s at the time.........but you know how nurses are, we tend to be terrible patients, and we take care of everyone else before we take care of ourselves.
The take-home lesson is, naturally, to listen to your body and obey it when it tells you to slow down. If you feel awful, STAY HOME! No job is more important than your health.........you don't have to feel guilty about that.
Hope you feel better soon!