Implantation bleeding

My husband and I just had sex. When I went to clean up, I realized that I had pinkish discharge. 
I'm on day 12 post ovulation and aunt flow isn't due until Friday. Do you think it's implantation bleeding or AF making an early appearance? Did anyone else have the same thing with their pregnancy? 
I took a pregnancy test last Friday, just because I couldn't help myself, but got a BFN. It would have been too early to test anyways, in reality. 
I need some insight! Help!