I will try to shed some light on what may be going on with you, but you do understand I am not a doctor or mental health professional, correct?
I believe one of the most telling aspects of your story is when you write:
"I have gone from illness to illness, thinking I get symptoms of many different ailments therefore in my head I must have the disease....."
Since you sound like a higly inteligent and articulate person, you must be aware that what you are describing is pretty classic hypochondria. Going from illness to illness is what hypochondriacs do. Besides the MS, I can imagine the number of diseases you have "contracted" over the past 12 years. As a "recovered hypochondriac" myself, I can relate and totally sympathize with what you're going through. Is there a particular reason you seem so focused on MS? Does someone you know actually have it? Have you been to doctors to rule this disease out?
That you feel an "inner" shakiness many of us can also relate to that, as that is also a pretty common side effect of anxiety. It doesn't happen to me as much as it used to, but I would think the whole world could see my shaking, yet when I'd hold my hands out, they were as steady as a surgeons! It was all inside me and I finally understood it was anxiety produced.
The murder of your friends husbands could indeed cause many of your fears to resurface. Such a traumatic event , I believe, can cause us to internalize many emotions that will then present to us in the form of hypochondria.
You speak of "emotional lonliness," even with lots of people around and that you sometimes let entire days go by when you accomplish nothing because of the worry you are carrying around. I think what you're describing here is depression which may or may not be primary or secondary to your health anxiety. They frequently go hand in hand.
You have stated that you've suffered with GAD for 12 years. Have you been treated for this disorder? Are you on any medications for this?
My humble (and again, non-medical opinion) is that you need to see your doctor for a complete physical to rule out an organic reason for your anxiety and then get into therapy to deal with the hypochondria/anxiety/depression cycle you're in.
There is a reason you suffer with this maladies and the sooner you can get to the root cause of them and begin to deal with them, the sooner you can regain control of your mind AND your life. I know how these issues can rob you of any pleasure and happiness. You've given this 12 years of your life. Time to draw the line, time to get really pro-active in your own mental health and get on with your life. There is nothing you've told us about that can't be "fixed!" But it's entirely up to you now.
I understand how difficult those first few steps can be, but I know that once you begin the journey to wellness, you will only become more and more motivated.
Your mind did this to you, your mind can undo it!
Please seek out help.
Peace
Greenlydia