I have also heard that it's not really necessary to culture for yeast because it's unreliable. Really, the reason the culture is important is to make sure that you're not dealing with something ELSE. I know for me, I was sooooo angry that I had been taking meds for the WRONG thing for so long, when the thrush was dead and it was mrsa. (all those unnecessary antifungals.... it still makes my blood boil. my poor liver! And the poor babies' livers!)
And I do completely understand that hopelessness when the tests all come back negative. Because then there's this sense of "okay. now what? Now NOBODY can help me". It turned out for us that it was a latch problem, and 30 minutes with a lactation consultant fixed it. Obviously, I'm not saying that will do it for everyone, but it's at least worth looking in to, especially if all of your tests come back negative. It could definitely still be thrush, but I'm just putting some other options out there.
I want to give all of you mamas kudos for battling this thrush demon so hard, and for sticking with it. I also want to share with you that YOU CAN BEAT THIS! It's incredibly hard, and for us it was over a year before we had pain-free nursing, between the thrush and all of our other issues, but we are still nursing, with no pain now, at 15 months! And I am so thankful that I found the determination to keep going, even on the days when I would just sit at the nursing pillow with a babe on each breast sobbing all. day. long. Believe me, it's worth it in the end. If your doctor can't help you, call an LC. See if your local hospital has a breastfeeding group; they are often moderated by LCs and you can get their advice for free. If your LC can't help you, call another doctor. Talk to other moms. Keep posting here. Try not to punch people when they tell you to eat yogurt. You are wonderful, strong, powerful mamas!