CD 38 and going crazyyy

My cycle is usually between 27-29 days, I have taken a pregnancy test the day AF was supposed to show, the next morning another test three days later and two test yesterday ALL are negative!! I don't get it why is AF so late!!!??? My life is the same I'm not stressed, nothing has changed I'm 22 and AF never did this to me only when I was pregnant she did not show up