I would continue with the big overnight pads for now & or the afterbirth diapers. They say tampons aren’t good for you. I’d also talk to your gp about your concerns.
A blood transfusion has nothing to do with the flow of your period. It's is common for periods to change after birth of a child. They will fluctuate again as your hormones level out. If it's concerning you speak to a GP
I would speak to your GP as that does sound really heavy. I’ve not had mine come back yet as I’m breastfeeding but mine have never been that heavy. I do love period cups and pants though, period pants might give you some extra protection with a pad.
For context this is baby 2 for me. My periods were not anywhere near this heavy with baby 1!