What I think we figured out is that we have "compatible" (co-enabling) anxieties that keep our relationship mostly functional. That feels like a drastic over-simplification but accurate, I think. All I know is it feels like the most emotionally productive year of my life and our relationship is way better now. However, I still haven't figured out how to tone down the anxiety much :)
Good news, you're completely normal. Every couple has their unconscious dance both in a positive and negative way.
Barring physical ailments, low vitamin D (etc), the solution for anxiety is do your healing work. Anxiety is often unresolved fear, anger, shame, guilt, etc. Everyone has anxieties, and they have to be dealt with daily.