How long do I keep testing?

Kristin

I was expecting af on or around July 21st. I don't always start right on the day predicted, but it's generally a 30 or 31 day cycle. I'm on day 45. I haven't missed a period in 2 years. I've taken several hpts and all bfn. Is it possible it's still too early to test? Should I call my dr? anyone else dealt with something like this??