try to pump only enough to releive pressure. also, feed only one boob at a time, and you can even feed twice if you lo doesn't drain one boob per feed.
cabbage leaves can reduce supply, bend them abit, then wear them in your bra. some babes don't like the smell tho'
avoid fenugreek, fennel and comfrey in teas or as spices/foods, as these increase supply.
it may take a while for your breasts to adjust, but if you hasve a trueoversupply, it is important to resolve...