My only thought was vasospasm. Do your nipples hurt when you get out of the shower, or when they're erect and unclothed? Dd had good attachment but used to slip a bit when sleepy, which was enough to cause some trauma to my nipples and helped create a vasospasm effect for a few weeks, where my nipples would sting everytime they were exposed.

A warm washer on hand before and after feeds really helpedcand keeping clothed as much as possible.

Google vasospasm and see what you think. Thrush is more painful i understand, but gee my nipples used to burn.

You're amazing