We had thrush for at least six weeks before any symptoms other than pain showed up. But the pain was really bad every time I nursed, and just getting worse. You could try some of the natural remedies mentioned by a PP, see if they help. I'm pretty suspicious in our case though that the thrush started when I turned down our water temperature. My MIL is very involved in daycare legislation/regulations here in NS, and she told me what the hottest temp allowed in daycares is, to cut down on risk of scalding, and, of course, our water heater was set waaay above that. So I turned it down--DS isn't turning on taps yet, but it's only a matter of time, he's into everything! Blam, thrush. I turned the water heater back up when we started treating the thrush. So far, knock on wood, it hasn't ever come back now that we're washing clothes in hotter water again.