Implantation bleeding!? HELP

Emilie
How long can it last?! 
​I got what I thought was my period a week early, except I have hardly any cramps, the blood started off light red almost pink, stayed that way for about  two days, and now on the third day it's started brown and is now back go light red. There is a medium amount of blood. 
​I'm sti unsure if it's implantation or my period. My period has never been late or early. 
​I have minor cramps in the middle area right above my pants line. 
​Any info would be helpful!