Implantation or irregular period?

I've always gotten my period heavy every month. This month it came 4 days early and is way lighter than usual. Although I do have cramps. I've had all the symptoms of my period expect breast tenderness. The color of the blood has been dark to almost brown at some points and at others it's been light pink. It's had little blood clots in it. I've had sex but it's almost always with a condom or its the pullout method. Any ideas?