Advice please 😁

So I am due to start my period tomorrow. I took a pregnancy two days ago and if was 100% clearly negative 😭. Sooo if I don’t start my period tomorrow when should I test again? I have no sign of af coming and I am hoping she goes on a 9 month vacation. 🤞🏻 lets just say she doesn’t come.... would testing tomorrow be an accurate answer? Also, how would I know if I ovulated late therefore starting later?