I completely relate to all of this.
Last year I was in a constant state of panic; I had a horrible feeling in my chest, couldn't enjoy anything and I tried various things like breathing exercises to get to sleep (similar to what you describe). I never knew what "chronic anxiety" actually meant until I had that experience and all I wanted was to be normal again.
During this time I had twitching that wouldn't go away. I was very disturbed by the twitching, as it is a sign of many diseases and I was scared it wouldn't go away, but I think it was actually a symptom of anxiety.
I now don't have twitching any more (or not often) either.
It might sound unbelievable or ridiculous (though it is no more ridiculous than the hypochondriac thoughts themselves), but I "cured" myself when reading on /r/healthanxiety how someone said they think something along the lines of "in this moment I will accept whatever disease I have, if I am really dying so be it, if I survive then I am okay". I just mentally banish the thoughts now with this idea.
Also, please do NOT Google symptoms! have self restraint about this, it's very important...