Cd36 - 5bfns - negativ blood work - implantation bleeding

C Momma
Heyyyyy everyone!!!
​I was wondering if anyone has experienced what in going through... Im 29, ttc for 9 months now. Regular 28-29 cycles. LMP was june 24 - This month i had what i think is called implation bleeding from july 18-21 (very brown almost black spotting) - took 6 hpts so far all bfn - decided to get blood work and also negative! Could i still be pregnant? And not have enough hcg to be detected by the tests? Help please! Where has Af gone if im not pregnant?!!!