I used to be onthe verge of tears contemplating the next feeding :P and I would have to bite my tongue not to cry out in pain from it.
Has an IBCLC seen if you have a latching issue? Latching is the primary reason for nipple pain and cracking.
My doctor didn't respond at all to my telling her I had lots of pain and all the symptoms of thrush--she told me the use a nipple shield, which is pretty bad advice. Many yeast infections have no increased redness at the nipple, my nipples are icy pale so I could tell the difference but my doc could not. After that I decided she would no longer be my doctor. It's terrible to let a bfing mother go through pain untreated. Inexcusable! Pain is the #2 reason why mums give up, behind thinking that one has under-supply.
After that doctor visit I went a third time to the maternity ward/obstretical emergencies and this time, ruling everything else out, they gave me 2 weeks of flucanazole, an anti-fungal ointment for nipples and my duaghter's mouth, and advised what painkillers I could use. I think they just decided that it was worth a try and I truly insisted. Bring a printout of thrush symptoms and check them off so they can see you're serious.
Word to the wise is that getting treatment with flucanazole frequently has less pain the first day, then goes back up to the 'normal' pain level for the second and part of the third days as the yeast start dying out in droves. All I can tell you is I soldiered on and did not give myself the option of giving up bfing or supplementing at all. Day 3 evening: phew, the pain went away and HAS STAYED AWAY! Bfing is really easy now. No bottles to carry, no sterilization hassles, no waiting for a bottle to warm up while juggling a screaming baby in your arms. Keep it up! You can do this mama!