It is possible that you have AF, although that would make you pretty unlucky. It could also just be a "bleed" without it being AF. After DS1 I thought AF had returned a couple of weeks after my lochia stopped. Luckily it wasn't, so don't despair yet. If you haven't had your 6 week check up yet, you could ask then, although it is unlikely they would be able to tell much. You probably will have to ride this out and hope you don't get another one in 4 weeks or so. Fingers crossed it's not AF hun, that would really suck.