First thing I would suggest is to have your IgG subclasses checked. 25% of people with autoimmune disease are also immune deficient. Since you get an infection every time you increase the immune suppression you might just have a weak immune system to begin with. Many doctors check the IgG level but they don't check the subclasses. MANY people (myself included) have a normal total IgG, but are deficient in 1, 2 or more of the 4 subclasses. This would explain why you have a hard time with your current treatment regimen.

You may find it helpful to treat the underlining cause...but sadly, it's not always effective for autonomic dysfunction. When autoimmune disease attacks the autonomic ganglia, it is often permanent. Therefore, symptomatic treatment is used. There are good treatments for gastroparesis, and orthostatic hypotension, along with POTS. The neurogenic bladder is a bit harder to treat, but hopefully they have some new treatments out there now.