This is really embarrassing, but if there is really no way, you must tell the instructor that there is nothing you can do about it. Some girls really pass out with dysmenorrhea. If it really doesn't work, you can explain it to the class teacher first, and then convey it to the instructor with the consent of the class teacher. If you are afraid of embarrassment, you can let your classmates tell the class teacher together. In this case, it will be fine. Drinking more hot water or eating brown sugar to boil eggs is very useful.