I'm so sorry. I had this with my fourth child and found the pain unbelievable. It was in the ducts and on the nipple and took quite a bit of shifting.
I managed to carry on feeding, and am really glad I did, but it was agony. I had to take pain killers all the time and couldn't even let the water of the shower touch my nipples.
The thrush stayed for about six weeks and, in desperation, I went to a homeopath. It cleared up within 48 hours of my taking the remedy.
If you prefer the conventional route ..... You have to make sure you're treating the baby as well as yourself (the doctor should give you nystatin drops). The Breastfeeding Network have excellent advice on this because Doctors aren't always clued up about how best to treat it and are out of date on recommended dosages.
I took out a print out from the BF network and showed it to my doctor who was grateful.
You probably know all this but I'll reel it off just in case ....
Cut out sugar, wheat and yeast completely for the time being. Take lots of pro-biotics (acidophulus bifodus from health food shop). Live yogurt put straight on nipples and/or eaten.
Put your nursing bras in vinegar or put a bit of vinegar in the wash they're in to kill the fungus.
Lansinoh is the ONLY nipple cream recommended by the Breastfeeding Network. It is very gentle, great for protecting moist wounds while they heal (cracked nipples) and doesn't need to be washed off before feeding baby because there's nothing nasty in it.
I highly recommend the BF Network. Sorry I'm still not able to do links.
You WILL beat this.
All the very best. x