Nine days late

Dee • married, four beautiful daughters

May have had implantation bleeding today or maybe one spot (literally, one very light pink spot) to preface my period, but that was at noon, and nothing since. Three negative pregnancy tests since the 15th. Anyone know when implantation bleeding usually occurs if it's going to? I never had it with my first three that I noticed and each time I've been late, I've been pregnant.