M.,
i've been through thrush with both of my children. What worked for me (and it sounds funny) is I would use the Nystatin liquid they gave me to rinse the baby's mouth out on my nipples after each feeding and after showers, etc.
I, in fact, used the Nystatin on myself more than on the baby.
also, i use cotton re-usable breast pads, and just change them out like 3 or 4 times a day -- means more laundry -- but that worked for me. also, don't get hung up on the instructions to air - dry, they won't fall apart in the drier and are softer that way anyway!
ps -- have you considered getting a second opinion? it might be a deeper infection of duct blockage, especially if the baby isn't showing discomfort or yeast in the mouth.
good luck!
PS -- along with what Karen said -- don't just eat yogurt, i know people who will put some yogurt on their nipples too -- you know it won't hurt the baby!