Lupus is diagnosed by having 4 of 11 symptoms. (Check out the link Diagnosing Lupus below.)
It sounds like your rheumy is progressing thru the necessary steps for diagnosing your issue. There are a number of illnesses that match the joint pain and slightly elevated ANA that you have. Besides blood tests, the rheumy should be giving you a long list of symptoms to check on - some of the possible symptoms for a variety of illnesses are subtle, so unless we check against a list we often don't recognize we have them.
Be patient and let the Dr do his thing -- it's a good sign that he's admitting a bit of confusion rather than rushing to a (possibly incorrect) diagnosis.
Let us know how it goes,
Lynnwood, Lupus & Sjogren's Moderator, Dx: 2002DIAGNOSING LUPUS & HW's LUPUS 101
"Life is far too important to be taken seriously." - Oscar Wilde