Why would you get spotting the day before AF is due?

Hi ladies! Ok AF was due today, yesterday has a tiny amount of brown jumpsuit when I wiped and less today now just pink wee when I wipe, clutching at straws here as Been TTC for soooo long and for the life of me I cant remember exactly how AF starts every month, I usually do have two light days then wham but this is different. Surely too late for implantation bleeding although I have heard you can have a very light period (couldn't call this that though really at this stage) as your body doesn't know yet to stop our periods? Any advice would be great ladies, oh and 6 BFNs in the last 7 days.