Period or Implantation Bleeding

Got my period 3 or 4 days early (never happens, it's usually on time or a day late), and it's lighter than usual (also never happens). Arrived with a slight mucous discharge and was a brown color at the beginning. Now, some of it is red/pink, some of it is brown, and the ""flow"" doesn't really even fill up a tampon at all. My period usually comes in a blazing glory: heavy flow and heavy cramps in the beginning... which usually fizz out by the 3rd day. I don't really have ANY cramps, and my flow is light. What is going on?