I thought I had my period back when my LO was 6 weeks, since I had stopped bleeding at 5 weeks PP. I got 4 days more of bleeding at 6 weeks, then it was gone. Then it returned at 9 weeks. I didn't understand why (I was only nursing, so I thought it would be longer) but I assumed it was it. But, then I NEVER got another period of any sort until 11 months PP, when regular cycles returned.
I was reading somewhere once that the changes in hormones up to a certain number of days can cause bleeding and its not a period. But I don't remember what it was called or where I read that.
Anyways, some women obviously do get their period back, but you can of course still nurse like others said! But it might not be your period. Time will tell.