Sorry to hear AF is back again so soon. That really sucks.
I doubt the BF is the cause of another period. But I would also doubt that you need to worry. If it were me, I would stop in and chat to the GP, but I am used to very regular cycles (I don't fluctuate by more than a week, unless pregnant of course). Probably they will tell you to keep an eye on things but they may have some more insightful questions to ask IRT other possible clinical symptoms.
So I reckon it's probably nothing to be concerned about but it's still worth a trip to the docs to have a chat.