Newbie Intro - Multiple False Positives? TW: Miscarriage, loss

RunningFromPessimism

Hi all!  I’m new-ish here and haven’t been active on the message boards in years but am back!  I’ve had three successful pregnancies, but while trying for our fourth we’ve had some trouble. 2 miscarriages and one chemical pregnancy within the past year, and now this odd situation, so wondering if anyone else here has had a similar experience.  

Two days ago I got a faint (but definitely visible, not an evap or indent line) BFP on a FRER test. My doctor had me go in for a hCg Quant which came back negative.  I assumed it was a faulty test with a false positive. I took another FRER test this morning (from a new box, just in case the lot was faulty) and got another faint (same shade as before) BFP.  I’m assuming I should trust the bloodwork that I’m not pregnant, but has anyone else had this happen?  What could be causing the false positive pregnancy tests?