Originally Answered: What is this illness?
Let me answer your question with a question. Suppose your problem is a phobia. You say it's fear, it's "scary." Some people are afraid of skyscrapers, walking down streets under them although they know there's no danger. What I'm saying is, maybe you don't have gloomy thoughts about life and the universe, but thinking about spiral galaxies scares you anyway. That would be irrational fear, phobia. Then again, maybe you do have gloomy thoughts.
The point I want to make here is that I can offer you some information that might change your point of view, but I'm not sure that it will solve your problem, at least not right away. Phobia is conditoned reflex. Maybe you need more than a different point of view.
There's a common misconception, that modern science has done away with God. While it's true that scientists aren't as religious as people in general, the number who are might surprise you. In fact, a Pew Research Center poll indicates that more than half of scientists believe in God. Studies of near death experience have convinced many that a higher power is involved with individual human lives. You can see a very interesting BBC documentary on the Pam Reynolds case study on You Tube.
I'll tell you something about derealization. The method can be used for stress reduction and anxiety.
At CalmClinic.com., they say
"Doctors and psychologists generally agree that the best way to stop derealization is with mindfulness. Mindfulness is the act of becoming more aware of your own present. Mindfulness can be completed in a variety of ways, but the easiest way is to simply get yourself to perform an action and focus as much as possible on that action in order to get yourself back into the world.
Touch something warm or cold. Focus on the warmth or cold.
Pinch yourself so that you feel how real you are.
Try to find a single object and start identifying what it is and what you know about it.
Count something in the room. Identify what they are.
Utilize your senses in any way possible."
You may find that you're more likely to experience derealization when you're passive and unable to do anything, like while you're sitting in a car passenger seat. Doing things attaches you to reality. If you're making a sandwich, do it consciously, Opening the lid of a jar, be aware of how it feels and what the jar looks like. Eat the sandwich slowly and enjoy it. This principle works with lots of things, like doing household chores.
This is another mindfulness method. Observe your emotion while you meditate on your breath. Awareness of the breath is important because it reminds you of the present moment and because its like a thermostat of your moods.
Find time to relax. Really relax. Lie on your back in a quiet room and close your eyes, then breathe slowly and deeply. Starting with the soles of your feet, be aware of the sensations of your body, going gradually from your feet to head, all the time being conscious of your breath. Spend maybe half an hour doing this. You may want to listen to some quiet music.
This is a stress-anxiety method I call Muscle, Breath, Mind. It combines methods from different therapy approaches. Suppose I want to make myself a sandwich. I get up and go to the kitchen, getting out of my chair without hurrying and walking softly because whenever I hurry, that tenses my muscles. Before I open the fridge, I think about what I want. I notice that I forgot to take out the garbage, which bothers me, but I take a few slow, deep breaths and remind myself that it's a minor problem. While I'm making the sandwich, I do everything carefully. If I feel any tension in my muscles, I relax. I get a radio station with music that will please me while I eat, just the right kind. I sit down and eat the sandwich slowly, enjoying every bite. You can find many uses for this method in daily life.
Originally Answered: What is this illness?
I would probably need “Additional Details” to answer this fully, but I will try to give you an idea of what some of the possibilities are.
You mentioned the use of Nitrous. If you have used drugs in the past, it may not be an illness but a type of brain damage. Nitrous would compete with oxygen in the brain and might even target specific sites or parts of the brain. If this is the case, you may simply be experiencing the result of damage that was done in the past. Now I know from watching documentaries on the brain that certain chemicals have been found to target specific sites in the brain and the conditions that are produced might then be given a name if others have the same symptoms from say the same chemical, but otherwise it may just be a conclusion that there is damage, but they don’t know what to do about it.
Now if you did not do drugs, (or nitrous), you may want to find if that is anything that you think or do that produces it. (If you can you probably can make big bucks!) COOOOL MAN! You may want to find out if you furnace is working properly. Because it may be producing carbon monoxide which can cause maybe something similar to what you are getting (but I doubt it!)
Well that is about all that I can say on it. But, I admit I am just taking stabs in the dark.