Re: Weaning from the pump
m11612 has given you some great information on dealing with a cow's milk protein allergy if you choose to continue nursing at this point (which is certainly still an option if it suits you). If not, then there are a few things that you can do to help with the engorgement while you wean. I have not weaned (so take this for what it's worth), but I can tell you some things I did to handle engorgement due to oversupply that can be applied to weaning. I think you can start shortening up your pumping sessions to encourage your body to make less milk if it is too uncomfortable to drop a session entirely (I would work on dropping one pumping session at a time). If you try to drop one session, then massage your breasts firmly during engorgement to avoid plugged ducts (it hurts, but it really helps). A firm massage in a warm shower helped work out stubborn plugs for me, but you shouldn't let the warm water run directly on your breasts because it can stimulate milk production. I found a lot of relief from cold compresses, and you can also try putting some cabbage leaves in your bra.
Here is a list of herbs that tend to lower milk supply:
Good luck with whatever you decide to do!
K. Sophia - Mama to my little lactivore, the amazing Mr. X (11/10).