Period or Pregnant?

So I got what I thought was my period. It started yesterday. Its so light its not enough to fill up a panty liner. Its brown and pinkish color. We have had unprotected sex. Not sure if I should test or if my body is out of whack. I have already had my first real period since I had my son. I posted in another area with no response. I'm 3 month PP. Any advice given is appreciated.