I would try weaning even slower, if you can. Aim for the 7 day range instead of 4 - or even longer, and if you start getting too engorged, pump a bit off - it will help avoid the plugged duct. Massage your breasts a bit in a warm shower to let off some extra milk, and you might try using cabbage leaves in your bra to reduce the engorgement. It will make the weaning process take much longer, but hopefully you'll avoid complications like plugged ducts or mastitis.