I know you aren't asking if Nutrasweet causes lupus... only if drinking it could make your symptoms worse. The only way to answer that question for you --- is to go off it a period of time (several months) and see if there is an improvement.
I have drunk diet sodas on/off for most of my adult life. I have gone on several lengthy avoidances of artificial sweeteners lasting several months to a few years as well. One time going off it made zero difference, and other times I do seem to feel a little bit better and flare a little less, but most of the time I don't notice much of a difference whether consuming it or not.
There have not been any studies done on this definitively proving or disproving whether Nutrasweet makes lupus symptoms worse as far as I know at least. There are side effects to consuming this for some people, most notably headache. This is almost like a drug after all, so you have to expect some side effects. There are others too but I can't remember what they are; you could look them up on a reputable web site (FDA perhaps). I know I saw that at one point in time.
5-7 cans a day is a LOT. Although when I was younger I would drink nearly that much myself too! It may be a good idea to cut that down some and drink water instead 3-4 times each day as water is better for you
