If you have lupus or not, leaking protein is not good, and sign of some kidney disfunction. I wouldn't worry so much about if it's lupus nephritis but just treating the leaking protein. I have switched many times throughout the years to different rheum when I feel they are no longer or we aren't on the same page as far as treatment. I am all for trying someone new.
I know about not wanting to take the meds again because you know you are taking something that will make you sick. That goes against human nature to put something in us we know will make you sick. But I have experienced a lot of very un-fun long processes to get well. At times you feel you are worse then when you started, but from experience, sometimes you have to go down before you can get back up and be strong again. Take your meds, you want to protect those kidneys!
I do know how hard this can be. I am sorry that you are experiencing this. But know that you are not alone in your fight to get better.