"Most people with lupus will have a positive ANA test result. It is very rare, but it is possible to have a negative ANA test and still have lupus. In these instances, other antibodies are present."
The ANA test measures a hodgepodge of antibodies together, but the other tests look for individual antibodies such as dsDNA and Smith. You should want a panel of those.
Annie is saying to check urine because kidney damage can be a very bad and irreversible effect of lupus. Protein in urine makes it frothy, but that's a late effect. Early detection of kidney damage is critical, that's why I'm answering here to say that urine dipsticks give early detection - and you can even buy them OTC for $10-$20.
Are you taking any prescriptions that would make you sensitive to the sun, such as doxycycline? Has the doctor tested your iron level?