progress

Thanks to everyone who has asked about how I'm doing. I really appreciate that! I've been hip-deep in getting my school work started for classes for the last week. Classes start today, but I knew I'd feel better if I could get a head start and not fall behind. Happy to say that I am ready to post all my assignments for the week today. :)
My neuro agreed that disability is necessary. I've never done this w/o surgery being involved, so I have mostly just not gone to work and waited for his letter. Today I am back in the office, though, to tie up some loose ends. Even thinking about work gives me anxiety and being in the office this morning, just walking in, caused me a full-blown panic attack. (Even now my heart rate is 132 bpm.) So I have no doubt that I am doing the right thing. This is no way to live. I called the neuro's office this morning and they located the letter and promise to have it to me today. 
So now all I have to do is figure out how to tell my boss that I can't keep working right now. They need my efforts to get work done and I will not be giving it. How to start that conversation? 
"Boss, we need to talk. You know that fall I took on NY day that I mentioned? Turns out it's a symptom of something much worse. The neuro wants me to stop working for now b/c it's making things worse. I am really sorry, but I need to go on leave, effective immediately. I have no idea how long this is going to last or when it will get better."
Or do I go to HR first? That might be safer, but much slower. It probably doesn't matter, actually. The outcome is the same: doc's orders=they have to comply and cannot do anything to me for it. So, all that's left to do is get the letter and print it. And email it to her and HR after I talk to them. I have a feeling I might be spending some time on multiple walks outside just to get fresh air while I wait through this day. I know the end of this day is going to be so freeing, though. Weight off my shoulder--or chest as the case may be.