Obviously, talk to your OB/Midwife/Dr about this. It's normal to get your period at just about any time whether you are nursing or not. I didn't get mine until six to eight months after I had my children when I was breastfeeding, but that was just me. If there is a lot of blood, soaking through a pad in an hour, then you need to go to the ER, could be internal bleeding.
I got my period back at around 6 weeks with all four of mine, even though I ebf on demand. (I had all c-sections though.) But it is normal to get your period when breastfeeding. Mine was regular and I was able to continue to bf for 2+ years.