CF - I didnt get AF back at all when I was bf DS1 - i was on the mini pill after 2 months but still never got it til I totaly stopped BF (and the mini pill as it happened as we began ttc notlong after).
I woudlnt stress too much abotu it, your bod can take ages to get back to normal... BUT if you really are worried just do it to know one way or the other IMO.