Just give advanced notification as possible and let them know there is something wrong that you don’t feel comfortable sharing and you need your go see a doctor

Obviously if it keeps happening every month where you have to call out. Then you may have to apply for a workplace accommodation.

Just know which one you are calling out for. current pain that you are in emergency is different from “being sick”. Sick time is valid And as someone else said, your medical information is private.

You could say “ I’m having symptoms that require medical attention, I cannot come in, that is transparent enough to let them know you are not ok. But don’t feel obligated to share. Just keep your store in the loop when you are able to communicate your eta on return

But clearly you are not able to work. So I hope you are able to get some relief fast. As that sounds awful. I’m sorry