Any advice would be greatly appreciated

I've posted a few times but possibly in the wrong section as I don't seem to be getting many replies. 
AF is 18 days late. I have taken a couple of hpt, but they are coming back negative. 
I have a doctors appointment booked but it's not until the 16th. 
I was wondering if this has happened to anybody else and if they've still got a bfp by the end? Or if it's time I just let go of the thought. Any advice would be amazing. Thanks in advance.