A Week Early

Hi ladies! I've been ttc #1 for about 10 months now. It seems recently, when we time things right with +opks, I start spotting a full week before AF is to arrive. 3 months now out of the past 5. Every time I get excited it could be implantation but every time it lasts the full week till AF. Kind of a bummer and I plan to go to the doctor asap but anyone else experience this? Thanks! =)