Breastfeeding... And pregnant again?

I am a breastfeeding mother of an 11 month old baby girl. 6 months after childbirth (October), I resumed my monthly menstrual cycles. My menstrual cycle has always been irregular. And I have also read that regaining a "regular" AF while breastfeeding can take awhile. I have been tracking my periods since October; however, for the past nearly 2 months AF hasn't revisited (last period was Jan 9-16). I did however have a brief episode of mucus with dark blood in it (Feb 24). I thought it was the start of my period, but it wasn't. For awhile now, I have been feeling cramps on and off. And I may have tender nipples? It's hard to say.