Spotting

Hi ladies!
I am 2 months postpartum and have been breastfeeding my baby. I've also been pumping & giving her breastmilk (sometimes formula) once in awhile through a bottle which I only do when I'm out or when I leave her with someone. 
This is my 4th baby but my actual first time breastfeeding (I have tried to breastfeed before but wasn't successful). Anyway, I've heard that when you breastfeed, your period may or may not come. Some can come right back and for some it can take months-up to a year. 
Well, this morning I noticed some blood when I went to the bathroom. I put on a panty liner to keep an eye out on the amount of bleeding and so far it's only spotting. Could this be my period or something else?  Has this ever happened to any moms out there?
Thank you in advance.