Confused

I had what I thought was implatation spotting on Sunday the 13th. Just like 3 spots of light pink when I wiped, AF was due on Tuesday the 15th. It's now the 19th and no AF. I had scant amount of brown discharge yesterday the 18th. Just when I wiped I send it in the toilet paper, thinking maybe AF was coming but today nothing... No spotting of any kind. I took a digital pregnant test and it was a BFN.  So I'm just curious if anyone has a BFP 5 days late for AF