I had implantation bleeding during my last pregnancy - got it 3 days before I was due on (CD 23) - got it one day, nothing the next, then the day after.
Im on CD 25 of 26 on CD 23 when i wiped there was a blob of pinky/mucky sort of colour CM and then the same yesterday and today and nothing other than that ive not a clue whats happening??
sounds like it could be ib then?... try not to get too excited yet though... just prepare to test, test, test!!