Freaking out about annual doctors check up tomorrow. ?

Its so weird how much my period can affect me but tomorow is my anual doctors check up for a physical- I think. Last time they checked my vagina and boobs but this time i'm on ny period :(. I really want 2 reschedule but I can't do idk what 2 do. How should I tell the doctor or what excuse should I use not to go. I really don't want to tell any of my relatives so I'm stuck in a mess.