Two periods in ONE month!

Charlie • 01-02-14💚| 06-09-15💙
So I am totally confused! I finished my period on the 14th of this month which was a normal 7 day period for me, but yesterday I had this brown discharge I thought nothing of it then it got a little heavier it was a pinky colour but it wasn't enough to fill a tampon or a pad it was just there, the flow isn't heavy it's light to medium. I've had a few cramps here and there and I'm pretty tired mostly all the time atm... Can someone help me!? Why have I had two periods in one month?