I can see why you worry about physical symptomsand feelings that many of us might take in our stride.
I think you are kind of pre programmed to react with fear and anxiety because of a sense that no one is there to look after you.
I get really anxious about my body when I am feeling alone and as if no one is there, and it's all down to me, and it feels like everything could just fall apart and no one would do anything so I have to be hypervigilant.
When I feel ok, and loved and secure (I mean deep down - not just from everyday things, things and people that are here for me now but deeper than that, from a long time ago) then I don't feel concerned about every little twinge because it seems like I'm safe.
So maybe that's where it comes from, a sense of not being safe for whatever reason. So you can't trust that you're Ok, and not really ill, or something, because you've no basis to trust that things are alright. That;'s hard to change as it comes from our earliest childhood.
So people with HA find it hard to get over.
I don't know if you have HA but maybe this helps a bit