What prompted me to test when I had my breakthrough bleed (which I had at night 13dpo prior to going to bed) was when I woke the following morning to no more bleeding/cramping as I assumed AF was incoming and as I'm not the type to stop and start with spotting (once AF starts that's it) I wondered WTF was going on?? Anyhoo..I cracked open a FRER and the rest is history.
You would get a definitive answer tomorrow....Just saying!!
Totally understand you wanting to hang on to BT though so will keep and sending prayers instead!!!xo