I feel i tend to overthink . Many issues, incl those outside of my personal life, like state of the world, society etc.

I have very analytical mind, since early teenager. Now, at age 44, i began to experience "Benign Fasciculation Syndrome",- frequent muscle/nerve twitches. These are believed to be triggered by anxiety, stress. But in my case, i cannot trace onset of these due to any higher levels of anxiety, if any.

So thus my question - is overthinking pattern ALONE can be categorized as anxiety? I am also, less joyful comparing to others. Its relatively hard for me to get into joyful mood, but i am also not depressed. I sleep perfectly well. Yet , all doctors I went  for help with these muscle twitches immediately say ITS ANXIETY. Without any psych. examination of myself. 

In the beginning of these problems i also had 3 episodes of what it feels like Isaac Syndrome, when twitches are much more severe and combined with hard muscle cramps. But Isaac is extremely rare, 1 in a million. 

Also, from late December up to few days ago (full 3 months) the nasty twitches went away, for no clear reason. And I have them only inside my home NEVER outside, which is totally weird, dont you think?

How can anxiety-based condition only manifest at home, and appear randomly with loong periods of complete absence? 

You have more experience with anxiety related problems than I do, please give me some guidance, suggestions...