FIRST: Let me say this..be thankful that, even without a diagnosis, you doctor is willing to treat your symptoms to help you feel better. That is a major battle won right there!
SECOND: Lupus is a very, very difficult disease to diagnose and the diagnostic process can sometimes take up to a year. During that time, if your doctor does not want to treat your symptom, you could become gravely ill and completely debilitated by the time a diagnosis is made. I cannot tell you how many times that has happened.
There are soooooo many here who have not been officially diagnosed or who have been told that they have undifferentiated connective tissue disease (people who have symptoms and some lab test results that look like a systemic auto-immune disease or connective tissue disease. But they don't have enough of the characteristics to fit the diagnosis for a well defined connective tissue disease, such as Lupus). Others are told that they have Mixed Connective Tissue Disease (meaning they are showing signs and symptoms of several illnesses, but not enough signs and symptoms to call it any specific illness).
I, personally, applaud any doctor who cares enough for his patient to know that they are displaying signs and symptoms of a disease and, therefore, he is going to treat those symptoms in order for his patient to get relief while they are trying to discover exactly what is going on.
Plaquenil is, for the most part, the first line of defense when treating disorders that are believed to be auto-immune and/or connective tissue disorders. Please know that Plaquenil is a cumulative drug, meaning that it must build up in your body before you will see significant results. This could take up to 3 months (that's why he said he'd see you again in 90 days). However, for many, once the drug does start to work, the results have been quite favorable. If, in that 90 day period, the drug has not been that helpful, your doctor may add Prednisone (a corticosteroid - nothing at all like anabolic steroids) to your regimen.
I do hope that the Plaquenil begins to work for you and that you start feeling better soon. Again, be thankful that your doctor is treating your symptoms. This means he cares and he is, at least a bit knowledgeable about the disease. These doctors are few and far between..believe me!
I wish you the very best.
Peace and Blessings
Look For The Good and Praise It!