Late but still BFN

This is my first cycle off the pill and trying to conceive. I'm usually a normal 28 day cycle. We tracked ovulation with clear blue easy & it estimated ovulation on the 17 or 18. BD all around those dates. AF was due Tuesday and is still a no show, but all tests keep showing a BFN. I always spot before AF, but have seen nothing. I have no other cycles off the pill to compare it to, & I'm so frustrated! Signs point to prego, but no positive test!