Hi Libelle, much empathy for your angst.
All I can recommend is that you may wish to consider a HPT as it can show a positive this early on and this might alleviate your concern regarding the spotting.
I did transfers of 5 day embryos twice, the first time the embryos were both more advanced than the second time and the positive showed up 5 days post the transfer. The second time they were less advanced, it was negative 5 days post transfer, I did not test 6 days post transfer and it was positive 7 days post transfer.
On the other hand, you may not wish to start the pee-on-a-stick roller coaster ride this early.
Thinking of you. Best of luck.