Sophie has already replied with handy information as part of our support.
Many years ago I had severe anxiety and the symptom I had was exploding issues in my mind well beyond what was a measured level. Paranoia? Likely, although that isn't a nice word I think it is exactly what it is. What was needed was therapy in my case for me to learn what I hadn't learnt as a child, to keep things in their proper perspective.
Some comments he made back in 1987 include- "Tony, when are you going to stop saving the world". "You might have the Whiteknight syndrome" and "There is 8 billion grey people in the world but your thinking is black and white".
So began my journey to change towards normal thinking. I'm no psychologist so bare that in mind, just passing on my experiences.
What to gain? Well I never did change my thinking radically. I do however stop to consider if my reactions are in proportion to the problem. If so I usually take a break, have a drink and think about the situation, often ask others of their views etc before resetting and returning.
I'm pleased you are planning to return to schooling. Anything in a forward motion is worthwhile regardless is you succeed or not. Keep moving forward.
A big influence on your forward thinking is your memory of your aunt and how you blame yourself for those events. Bare in mind the events that led up to your intolerance for coughing, sniffing etc is no different to those intolerant for loud noise, dogs barking, train sounds, jet engines and so on. Your condition is a medical one so blame is not helpful. Move forward, focus on short medium and long term goals and get some more professional assistance is my wish for you.