Period before time

Ok I've been trying to get pregnant the past few months, and Tuesday was my fertil day so I've been have sex with my husband every other day until we got to Tuesday but on Wednesday morning woke up and had this brow discharge with blood on it dont know what it is could it be my period or a miscarriage can any tell me, I don't usually get my period this early usally it's late by 2 or 3 days but never this early the calender says I will have my period on the 18 not the 4... help please should I go to the doctor or just wait and see?