I'm in the UK. I tried to drag an email from my HR department out, but I can't find it.
Anyway, we come under the disability discrimination act. as long as you have doctors notes and have been honest with your employers, they can't fire you and have to make special considerations.
I had a whole year without a flare and was diagnosed in 2010, now i've had a few days off here and there recently. I have to fill out annoyingly long forms, but its all to keep it covered. When I was first diagnosed I had 6 weeks off and couldnt explain why to start with, luckily my company has a nurse who explained to my managers what a cronic illness is and now my managers know when I say "illness related" not to really ask much more
Also go to the citizens advice beuro, that's why they exist.
If its getting worse, go see the GP again and see your specialist ASAP. Usually if I call the hospital they can get me an appointment within a few weeks and once the next day when it was urgent.