Hey Lisa
I tested on d14 and d15 dpo and got BFNs which was the day before and the day suggested by FF. With that I'd given up hope and my temp dropped on d16 so I just waited for AF. Two days later AF still hadn't shown up so tested on d18 and got a BFP. It was kinda nice to give up hope - coz we got a really NICE surprise then.

Shan have you tested???