I can only offer you support as I am in the same boat without a diagnosis , also the crazy thing , my doctor told me I was mentally ill and it was all psychological symptoms , so I really do know how you feel, I know you can have lupus with out butterfly rash or swelling joints so don't despair you could still have lupus , I wish you luck keep us posted !!
My GYN is the first who mentioned Lupus to me way back in 1998 when some of my first symptoms started after having a very serious infection (Group B Streps turned septic).
I've had a neg ANA throughout the years but all kinds of symptoms but still no dx because most dr's go by the thinking Pos ANA is Lupus, but not always true.
I developed Vasculitis in 2014 and sent to a dermatologist who was appalled that no dr had dx me with Lupus and did biopsies which were positive for SLE. (I forget the terminology)
Maybe a 2nd opinion and ask for biopsies that may help with a diagnosis?
hope you get some answers, I know for me it was 17 years of frustration.
Sorry you are going through this and feeling frustrated. It's understandable! Getting a second opinion may be something to consider or seeing an specialist such as an immunologist, endocrinologist, GI doctor (for GI issues) and dermatologist for the skin symptoms.