No one can diagnose on a forum but what you're explaining sounds like common symptoms of anxiety and OCD and the over thinking that comes with that. Fear of dying (and deterioration on the way to dying) are the case of all of my phobias. I have body dysmorphic disorder, hypochondriasis, panic disorder, OCD, perfectionism, etc etc. But I know the root cause of absolutely all of it is fear of losing control, deteriorating and ultimately dying. As there are many ways to die, or lose control/have your only connection to this world damaged or incapacitated, that opens the doors for many different phobias and obsessions if you are anxious/obsessive.
29, female, health professional, divorced, INFJ.
Medical Dx - BDD, OCD, Panic disorder/GAD, Depression, Perfectionism, Alcoholism, Derealisation.