Confused.

AC • ?
So, I was two days late on AF (started oct 13th).  It started off brown/pink and spotting. On the 14th it turned more red. Finally today, it was barely brown when I wiped (early this morning and later in the afternoon it was gone). I had sex tonight and now I'm bleeding again. 
​What the heck is going on?! Has this happened to any of you?