3rd month TTC and BFN

Joana
This is our third month TTCing and I'm currently 12 dpo. AF due in 2 days. I don't feel like this is my month but had a HPT this afternoon and it was a BFN. I was wondering: did any of you girls had a BFN at 12 dpo and then a BFP a few days later? Need some insight... Thanks in advance!