Why Is My Post-embryo Transfer Blood Test Scheduled 21 Days Later, And Does A Negative Home Test At 14 Days Mean Failure?

I have done fresh embryo transfer on 22nd of September but still waiting for blood test which my doctor has scheduled on 12 th of October i.e after 21 days . What can be the reason for such a late date? I have tried test couple of times in home pregnancy test after 14 th day but it seems to be negative. So do I consider it to be game over? No pain nothing after 7 days except for the palpitations also loose stool for couple of days. Please help