Welcome to the forum GBS
I am sorry you feel so unwell but glad that the Plaquenil seems to be helping already. We do like to have names for our diseases, although not being formally diagnosed is a Good Thing because an SLE diagnosis has serious implications for insurance.
Since your doctor started you on Plaquenil he must think that you have an autoimmune connective tissue disease. You seem to have enough criteria but some doctors won't diagnose SLE unless there are specific lupus signs. If there are no specifics for any of the A-I CTDs the diagnosis of Undifferentiated Connective Tissue Disease ( UCTD) is sometimes given.
Plaquenil has so many benefits apart from the obvious ones, it is almost beyond belief. Like any drug the list of possible adverse side effects is huge. It is a question as with all drugs of weighing the possible benefits against the possible side effects. The overall benefits of Plaquenil far outweigh the possible side effects which are in any case highly individual.
According to Dr Wallace Plaquenil causes leukopenia and anemia in less than 1% of those taking it.
You are almost certainly being regularly monitored with blood tests that will show any problems arising as well as to track improvements and the effectiveness of the drug.
Anemia of chronic disease is fairly common and can be expected to improve when the disease is under control. There are indeed many causes of anemia and more than one type might be present in one person. It is amazing how often the easily remedied sorts are missed especially if they develop after diagnosis. Presumably that's because when you have lupus all symptoms tend to be put down to the lupus especially by GPs. Fatigue of course, weakness, peripheral neuropathy and even cognitive problems can be caused by anemia. Ask your doctor about taking a Vitamin B supplement and to investigate pernicious anemia or B12 deficiency. A supplement can often make a difference even when there's no detectable deficiency. As far as I know any excess is excreted because the B vitamins are water soluble.
There are other possible reasons for fatigue. I am not sure, but I think men can suffer thyroid conditions even if it is unusual. Fibromyalgia with disturbed sleep patterns is another possibility. Presumably you have been checked for diabetes. Depression and anxiety are a common cause of fatigue, lack of interest and general blah. It can be caused by the disease itself as well as an understandable reaction to the effects the disease is having on your life.
If you are in the USA you could ask for DHEA levels to be checked. They are commonly low in lupus and supplementation to normal levels can increase general well being.
There's another antimalarial called Quinacrine in the USA and Mepacrine in the UK that can be very usefully added to the Plaquenil. The combination therapy is not as well known these days as it used to be but it can be very effective indeed for joint aches and fatigue as well as general disease remitting effects.
All the anti malarials are cortical stimulants but Quinacrine is especially energising.
It takes a long time to cope and adapt to having a disease. Realising one's limitations, prioritising, not getting overtired and learning not to reproach yourself, to name but a few realisations and understandings, are very necessary to successfully living with the disease.
Remember that all those who live pretty well normal lives with their symptoms well controlled do not usually post on forums!
Bye for now