Scant brown fluid

Well my friends.  I urinated later this afternoon and when I wiped noticed scant brown drainage and now I worried.  I had a 5 day blastocyst transfer and 2 morula stages (1 day behind) and should have implanted in 1 to 3 days so now it's day 7 and I'm thinking to late for implantation bleeding. Any advice or has anyone experienced this before and still had a BFP?!