i had a scare with my eldest, it was like day 6 or so.. it was a clot the size of a 50c blob. I rang the maternity ward of the hospital and asked.. they asked had i soaked a pad in a small amount of time? nope... then they said it was probably just blood that pooled and nothing to worry about (unless my flow got heavier) it did make sense to me about the blood pooling as i was sleeping and had just gotten up.
With DD2 my flow would change daily.. id go from thinking oh yay anyday it will finish to drats its red and heavy again *sigh*

Sorry i dont know how long that goes on for! Surely someone will answer with that soon