What do I do about a constant fear that prevents me from doing anything?

It sounds like you could benefit from some therapy with a psychologist. I'm willing to bet that it does have something to do with your disabled vet ptsd. Did you possibly have some traumatic experiences that make you have these constant fears? In sometimes extreme and emotional situations, we have a hard time coping with these memories, so we repress them and they end up manifesting themselves as other symptoms. Hope this helps, good luck.