What is this?!!

Sharnie

So I've had this in my knickers for the past few days now. It's not enough to wear a pad, that's from a whole day. I stopped taking my pill 6 weeks ago and no period as yet, me and my partner are currently trying for a baby, the most recent test was three days ago and was negative. What is this? My periods used to be so heavy! Surely this can't be it!!