Implantation or withdrawal bleeding?

Well i have been on BC PILLS for the past few years...I just changed my BC PILLS and i am on Yasmin ... I have been ovulating for my past few periods I am a non compliant user of BC PILLS ... i try to take on time never can always forget .... but enough of that well i have been ually active this month and i just so happened to ovulate that night 8/23/08....and ..so i stopped taking my BC 4 days ago because if you do you should have withdrawal bleeding...almost the same day...well that was 8/26/08 and 8/29/08 i have this tiny spec of brown in my mucus and only when i wipe .... other than that nothing....would you suspect implantation bleeding or withdrawal bleeding....its still to early to test i am one week away from my period .... please someone help a worried anxious mind