I don't suspect physical causes of how I feel unless I've been sick or am taking certain meds with known side effects and the anxiety coincides with taking/not taking them, etc. Anxiety is just extremely uncomfortable to me but I don't think of it in terms of being "sick" so I look for soothing things that I like that make me feel better (shower, clean sheets/clothes, warmth, good book, comfort foods, looking at the specific anxiety topic and seeing if I can "do" anything about it. I have trouble in the middle of the night but sometimes a couple slices of toast helps :-)

The best thing for my anxiety was 9 years of good therapy, 1996-2005. My middle-of-the-night stuff now is mostly existential angst (I'm getting "old") and the result of my thyroid replacement not working as well as it might. But before my therapy was over, working on a long project (school) that I really enjoyed helped a lot too.