Implantation or Early Period?

So my period has always been every 31 days **on the dot!**, never fails! It lasts 4-5 days, but never less than 4. Well I got my period 5 days early this month and it only lasted 2 days. It was VERY light compared to my normal period and (TMI, Sorry) when I took out the last tampon there was barely anything on it after 7 hrs just reddish brown and a little bit of light yellowish mucus (this is a first)... Could this have been implantation bleeding?