Someone please help me understand this...:(

Ci
So I had AF May 7 - 13th and then thought I had fertile week the 15th through the 20th. Well Friday I had light pink very little spotting and then some brown on sat. Did BD in sat and afterwards it was heavy brown spotting and now it is bright red and fairly heavy. Is this AF again? I thought at first it could be implantation but now I'm so disheartened and sad :( my bbt has stayed about the same so had my CM...what's going on? I'm never going to get pregnant if AF keels being a bitch :( :( :(