Extremely irregular.

Well this month my "period" came a whole week early. Or at least I think it was. From everything I've heard about what would be implantation bleeding it should just be one to two days of light spotting. Well it was one day of dark brown followed by three days of light brown. Seems a little long for that but my concern is if it is my period what would cause it to come so early and be so very light. I have a doctors appointment in a couple weeks but any insight ahead of time would help.