Period??

I am so confused, i had my baby girl 4 months ago. I couldn't remember when my last period was so I was waiting for it, ive taken 6 tests throughtout the last few weeks all BFN. Well I started my "period" a couple of days ago, it was light. More like spotting. Well it lasted 3 days and yesterday it ended. Well today it started up AGAIN. What the heck is wrong with me? My periods are usually heavy!!