12 days postpartum and sudden gush of blood

I’m 12 days postpartum after a cesarean. My bleeding had all but stopped. I only had brownish discharge. Then suddenly I got a huge gush of blood (darkish red, not bright) and I was completely shocked at how quickly it came out and how much. It’s slowed down to what feels like a heavy period with some moderate cramping.

Has anyone else has this happen?

I called my OB and they said it was completely normal but to watch for filling a pad an hour. I’m still a bit freaked out though.