I had my third section 3 weeks ago. I bled for the first week and not at all after that. The midwife did say you can bleed on and off for 6 weeks so not be suprised if I did again. Anyway, today I started bleeding again and initially it was like a gush - it seemed a huge amount in a short space of time. IT has since tailed off, starting and stopping again, but not in such large amounts. I have been having period type pains all day and now there is a sharp pain on one side of my abdomen.
I had 2 csections and found that as soon as I started doing more (especially after dd2 as runninga round after dd1) I'd bleed again, heavy then tailing off, it would be quite red then change to brownish over 24hours
You can get a clot of blood holding back fresh blood, which can then be released. I had this with DD2, sudden gush of blood. Went to hospital, scanned next day - nothing to see. They said that had I gone the day before the bleed, they probably would have seen the blood collection.