I can't work like this

Portia
My period chooses terrible timing to start. My period practically always starts when they schedule me to work on the register (i normally work in the office). And the first two days of my period I can hardly get out of bed. I be in immense pain. I usually call off from work when I start because I once went to work on the register when I it was the first day of my period and I almost fainted. Now my period started and I'm scheduled to work on the register tomorrow. But every time I call off my boss comes up to me and snidely remark "I see you called off again". And this boss takes no excuse.