What I read was that implantation happens anywhere from 3 to 10 days, so I imagine it's possible! With your cycle being irregular perhaps you ovulated earlier than you think? My understanding is that ovulation spotting usually lasts just a day or two whereas implantation bleeding is more like 4 days or thereabouts.

Having Mischelwurtz (sp?) and then bleeding 2 days later sounds like ovulation but is it possible that it wasnt mischelwurtz at all? I've had a sharp pain in my ovary before and I'm certain I wasn't ovulating as AF came about 7 days later (and theoretically, you ovulate 14 days before the start of your next cycle).

Have you thought about going to the Dr? Maybe they would do a blood test or something? Or have you done an OPK? If you've already bled though than it would probably be negative either way if you did now.