Should I or should I not? Need some advice, ASAP!

Okay. I have the most regular period I have ever seen. For four years, I start every 3rd. Even after my premature son and both miscarriages I have still started on the 3rd. I have taken 12 pregnancy tests in which they all came out negative. But my period did not come today! I only have pink show and that39s it. But my cervix is low and firm... I can39t tell if I am by my bbt due to it being as crazy as it is... As you can see in the pic below. So here39s my question.. Should I, or should I not go buy another test?