If you find definitive answers to those questions you will greatly further Lupus research!
Basically, no one knows why we get Lupus or what might cause it. We kinda' all believe that stress (mental, physical, spiritual, whatever) can contribute to it, but there is no scientific evidence to answer any of your questions.
Additionally, your situation is made more confusing because some (many) Drs are happy to diagnosis on symptoms alone, while some stubbornly cling to the idea of a blood test. The Lupus Org and the Rhemy folks all say you need 4 of 11 symptoms, only of of which is the blood test...so some Drs may have diagnosed you back in the past just by symptoms....
All we can really do is be aware of how we feel in the present and see that our Drs give us symptom relieve, with or without a formal diagnosis. Fun, huh?
Lynnwood, Lupus & Sjogren's ModeratorDIAGNOSING-LUPUS & LUPUS-RESOURCES
"Life is far too important to be taken seriously" - Oscar Wilde