I am in the EXACT same position with my 11-month-old. For me, it isn't thrush, she is actually latching on teeth first; I've almost passed out from pain! I called the lactation consultant (Emma Davis @ Kettering Medical Center if you are from the area) and she recommended Dr. Jack Newman's Nipple Cream. You have to get a prescription for it and get it compounded. The Medicine Shoppe compounds medicine and they called my OBGYN to get the prescription-- Emma Davis gave me the ingredients and I called the Medicine Shoppe first. I was not able to get it filled b/c of our co-pay (it would have cost $65.00) so the pharmacist gave me a combination of over-the-counter stuff that was similar. I don't have the ingredient list with me but if you would like them, send me a message and I will find them for you.
Emma also recommended Ameda Comfortgels (http://www.amazon.com/Ameda-17262-ComfortGel-Pads/dp/B000...) I have been using those and they make me feel a little bit better.
I know this adds up money-wise but as you know, the pain is unbearable and, at this point, I am willing to try anything.
I wish I had other suggestions for you. I have tried changing positions, too, and at this point am just trying to avoid the major holes in my breast-- and I do mean holes. I lather on the lansinoh and have cut down on nursing to 3-4 times a day. She turns one on Friday and, this sounds awful, I am hoping she just magically stops nursing; my first quit cold turkey three days before she turned one. Good luck and, if you have time, please shoot me off a message if you find something that works for you!