To your overall question: the ANA test does not necessarily go up and down accordingly as the disease gets worse and then better again. But is is not true that once it is negative, it will always be negative.
Butterfly rash? Hi, I'd say that you should definitely go again - ideally when the butterfly rash is showing. Or at least take several pictures in good light. You also probably have new onset Raynaud's in the hands. Have some pictures of that, too.
You can check in a mirror for any mouth sores. It also wouldn't hurt to ask the doc for a blood test to make sure that your kidney function is okay.
It is even possible, though rare, to have a negative ANA test yet still have lupus.
There is a sort of subset of the ANA test called the anti-dsDNA antibody test. Docs normally won't do that test if the ANA test is negative - but if the doc thinks that your symptoms really, really look like lupus, then the doc might do that test as well as another called anti-Smith.