how many days after af is due can you still get a bfn but really be a bfp??

[wishfulthinkingmaybe]

Just that really

Mine was recently ten days late for no apparent reason :( but fingers crossed for you.

i got a BFN a day after my AF was due. but 5 days after that initial disappointment, I retested (on the advice of people on this thread, who suggested I'd had implantation bleeding) and got a BFP! I don't know if that helps you at all, but best of luck!