Hi
firstly welcome to the club .. we all have (yes, the thousands of us, perhaps millions world wide) this problem. It can be fixed and you will go on.
Next I want to say basically just stop it ... what you are saying is just the express train to madness. It is anxiety it is irrational and it will just lead to you becoming mentally ill. So just give yourself a quick slap.
We all tend towards these thoughts but if you tend more towards it, then it is dangerous, its like a slippery hill, you step on and down you go with almost no return. So really, when you feel yourself thinking these things - stop it.
Its good that you mention here that you are feeling this way, and not pretend you are not feeling that way, but control it. Do not let what amounts to a mental 'neural' virus destroy you.
Sitting and wondering what if is the most unproductive negative irrational thing you can do. Just stop it.
What if a wheel fell from an aircraft and hit your car?
What if a meteor hit your house?
What if a rabid dog bit you?
(insert a million more possible and equally unproductive thought)
It goes round and round and round and round and only accelerates ... so just stop it! Stop it now.
I'm guessing that you are suffering from the shock of discovering "we all die" ... guess what? Those movies with funerals weren't fiction. That saying about "death and taxes" ... well its based on fact.
Humans all have some level of denial innate in their character. But the denial of the possibility of death seems to be the most curious. People seem to be so effective at it (especially in this polluted modern culture when its focus is selling you "stuff") that when they actually become aware of it they panic.
If there is a goal in life it is to become stronger, fitter, healthier and wiser. Death is certain. Learn to accept that and learn that well. From there you will find the path to peace and to not be traumatised by your imaginations.
The only monsters under your bed are the ones in your mind.
Get the book Dune (not the movie) and read it. That will give you some more to think about when these fears arise.