Twitching alone is not a symptom of anything. If you have been twitching for 6 months and don't have significant other symptoms you may likely have benign fasciculation syndrome. One of the common features of benign fasciculation syndrome is that the patients are convinced that they have ALS and often refuse to believe their doctors.
If you had a sudden onset of widespread twitching and a clean neurological exam, you probably have BFS. You might want to check out the following site to read some of the posts there and see if these people sound like you. There is also a good post called BFS in a Nutshell which kind of gives an overview of the syndrome.
The site is aboutbfs.com (it's another site like this, but for people with benign twitching. It's not my site, and I have nothing to do with it except that I post there).
I know that twitching is difficult to live with. I have constant, bodywide twitching myself, but knowing that there are others out there going through the same problems and fears who have been properly diagnosed with a benign condition may help to bring you some peace of mind.
But you also need to really address the anxiety. Most of us don't want to admit it, but anxiety rarely just goes away on its own. If you are this anxious, please seek help.
