If the thrush treatment isn't working, or working on and off, you might also have an underlying bacterial infection. My nipple pain didn't go away until I took ABS AND nilstat cream on nipples at same time. Each by themself didn't work.

Also a friend had chronic thrush which only went away after she stopped using disposable breast pads and started using only cloth ones. So if you're using sposies maybe switch to cloth for a couple of weeks and see if that makes a difference.