I thought thrush was something you got in your mouth? I swear I had something like that a while ago but it was this horrible... shit in my mouth... Ugh, I feel for you, that must suck royally. :( Yes, go see a doctor. Like, now. Even if you think you could be wrong, you could have some sort of infection, so you should go get yourself checked out.
I thought it could pop up by itself as a natural yeast infection or something. If you haven't had sex it can't be anything bad..I think p: plus i remember seeing "thrust relief" ads on tv, so you could probably buy some from the pharmacy without a prescription (but only if you know what it is)
Thrush is completely normal for people pretty much 16+. It's not sexually transmitted, and you don't really need to go to the doctor about it, unless it's been a few days after taking meds and it doesn't look like it's going to clear up.
It is, as Luminous said, your body just producing too much yeast, and this is the result of it.
Pop down to your nearest supermarket / pharmacy and pick up something for it. It's usually a cream that needs to be applied and a pill :].