My period was a week early and last 3 days and now the 4th day just brown blood. could this be implantation bleeding or just a early period?

Implantation bleed: Implantation bleeding is much more common on the internet than in real life. It occurs rarely and exclusively in someone who is pregnant. The only way to know if someone had implantation bleeding or just irregular menstrual bleeding is to wait and see if you are pregnant. If your test is positive then this was implantation bleeding. If it is negative then it is just irregular menstrual bleeding.