13 days past AF . BFN pregnancy tests?

Heres my story ... my period is always on time. This month it has not made an apperance. My and my SO have been having sex almost daily. No other method of birth control besides the pill which is very possible that it was failed to be taken properly. I have been takig a pregnancy test about everyday since I figured out I was late.. every one of them was negative. Im not sure what to believe anymore. The only time I have ever , missed a period was when I was pregnant with my son. Anyone ???