My goodness you've been through a lot already! Congratulations on the birth of your baby and on your hard work as a mummy so far
This is not the end of the world. Give yourself a break, ok? I mean that literally and figuratively. Can you pump for some time out, or take a break one feed a day and give a bottle? Sometimes when it all seems to much it's good to take a step back and have a time out. Or just approach this one feed at a time, don't look too far ahead - that just makes things seem harder when times are tough.
Go get a 3rd/4th opinion on the thrush - it can be incredibly hard to shift sometimes, but sometimes it might actually not be thrush at all but something else. Perhaps the nipple specialist will know.

It's great to hear how well your little one is doing, good work! Being a mother is very hard work, especially in the first few months. It doesn't matter how you feed her, it'll still be hard and you may still struggle. But it does get easier. Everything that challenges us passes in time and we move on to the next thing. Just feeding can be so hard at first - I know it took nearly 3 months for everything to fall into place with my first - but in time it becomes old hat.
Hang in there