8 days late... BFN??

Since I removed my implanon back in February 2015 I've had a very regular Cycle, 27-29 day.  Now all of a sudden I'm at 37 days or 8 days late. I could of sworn I was pregnant. I took a couple of test and all BFN. What's going on???
Symptoms: sensitivity to smell, tender to the touch breast, lower back pain, & tired. I had some mid-cycle cramping which never happens as well.
01/02/16
 01/05/16