Ugh, Claire - I am sad for you reading this. What is the autoimmune that you have?
When I was diagnosed with colitis, they wanted to put me on this but I refused because of all the side effects and just decided to drastically change my diet. Although, I have no idea if that would even work for you but probably best to listen to the doctors.
I do remember when my kids would get croup as kids and couldn't breathe right, they would give them this and they would be WILD - running around like crazy. So it makes sense as to why you can't sleep. That just sounds awful. I have a hard time with sleep a lot too... so I really feel for you!