All signs seem to be pointing to "I'm pregnant", but the HPTs have all come back negative. Is it possible that I am pregnant, but my HCN hormone levels are simply too low to be detected by HPTs?

Here's my chronology of events:
* My peak fertility day was March 13th and I had unprotected sex on the days before, during and after the 13th.

* I should have gotten my period on the 21st, but instead I had what I think was implantation bleeding on the 24th. It was very light, pinkish in color and lasted about 2 1/2 days.

* I have lower back tightness and my nipples are sore. I don't have nausea, but I feel queasy and a bit lightheaded at times.

* My period is now 12 days late and I am normally very regular.

* I have taken 3 ClearBlue Easy tests and 2 First Response Early Pregnancy tests... all AFTER my missed period. Five tests and 5 negative results.

Have you had a similar situation and you were actually pregnant? As a precaution, I have cut out caffeine, alcohol and sushi... and wake up every morning hoping that a plus sign or double line will appear, but it's either a minus sign or a single line.