BFN after 1 week late, anyone else?

I am never ever this late! I have gotten two BFNs both taken after my expected period. I do not think I am pregnant. In my experience no means no. But I am worried about this period being so late because we are trying to conceive for two years with one miscarriage and one thing I can always count on is my healthy cycles. All my fertility testing has come back with no problems. (I should mention we have one 4 year old daughter together). I have been stressed but not anymore than I have been before and still got a periods. Not stressed about conceiving just other things. Honestly haven't thought much of conceiving this last cycle at all. Has this happen to anyone? What was the result?