You asked for unusual circumstances and I think everyone would agree my case is fairly unusual!!
I tested early as usual and got my faint bfp at 10dpo (approx! don't know when I ovulated this month) and got them for a few more days but then got a Not Pregnant on the digi

I started to lose hope and my lines were getting fainter.
For the last 2 months I've had the same thing, and both ended in an early loss so I assumed this one was going to same way. Just waited to miscarry so didn't bother testing again. Then one night this week, I was up all night and couldn't get to sleep. It occurred to me that I'd been getting twinges and flutters all day, so I just decided to test again. Two lines came up on both tests within ten seconds! Did a digi in the morning and got my 1-2 weeks! So weird!
Keeping my fingers crossed for this sticky bubs to hang around

xx