When can I test

Hey ladies...I'm due for AF sat the 15..I literally have tested all wkend and this wk like a nut job..I just tested tonight on a test that says find out before 4 days ur expected period...I'm was sadly negative..should I give up hope and just say this is not my month? I ovulated on the 1st not exactly sure how long my cycle is its just so irregular ..help please I'm making myself nutso