Implantation bleeding or early period??

Brooklyn

I’m not suppose to start my period until Jan. 1st but I woke up today to light bleeding. Me and my SO just had sex 8 days ago. The bleeding was a brownish color and light, definitely not like my regular periods. And I’m a whole week early and I never start early or have 2 periods in a month. I’ve had what it feels like to be ligament cramps (I know because I have a 1 year old). Just really confused. And need some opinions