My wife has a mystery condition that flares up every few months / years. Every time it gets bad enough, the doctor prescribes antibiotics and then runs some tests. When the test results come back 24hr later, the conversation is always the same: "I thought it was [a very common problem], but the test results ruled that out. Since you already started the antibiotics, you should finish the course. Call me again if the problem gets worse."

So we're left without answers and with an unnecessary prescription for antibiotics, every time. It's pretty frustrating, to say the least. The internet has come up with "interstitial cystitis" as a possible culprit, but it's not much of a diagnosis with an unknown cause, no diagnostic test, and no peer reviewed treatments.