Af or pregnancy???

Marie • ttc our first child!
I calculated all my past menses and have calculated that I have a 26 day cycle! That being said, Af was actually due today and so far nothing. I have what I think feels like cramping but it feels more like stretching in the lower part of my abdomen. I tested this morning and bfn;( my cervix is low, med? And firm and my cm is dry...Af is coming isn't she???...dirty witch