Here's a thought, and something I've noticed with myself when I've pumped and not nursed directly. The pump isn't as effective as the baby with extracting milk from the breast. We all say, but this could be a point where it comes into play. Is it possible the pump did not drain you as much as your baby has, leaving you engorged for the next session because your body is use to more being eliminated by your baby? Like when you skip a session you will become engorged by the next session it doesn't mean you have an oversupply, just that today is different than yesterday. Just a thought. It's happened to me, like when my son went through a nursing strike. I still pumped as much but by night was engorged from never having him at the breast. Went back to normal the next day.
If you obey all the rules, you miss all the fun. - Katharine Hepburn