This sounds like anxiety. Don't hesitate to talk to people if it gets too tough to deal with. I have social anxiety (mostly with a large number of people, and dealing with strangers), and hypochondria (wondering if I secretly have something wrong with me and will die in my sleep) and I've started getting help for it (therapy and medication) and I'm starting to feel better. So trust me, I know where you're coming from.
Mine is dying on the toilet. I mean just imagine that someone finds you dead on the toilet
mine's a lil weird, my worst fear is to "fall", but it has many meanings, for example:
-afraid of elevators because they could fall
-afraid of unsteady places or feeling unsteady (when someone carries me), makes me feel like i could fall, like glass floors
-afraid of people having expectations, the highr they consider you, the wors will feel when you fail (fall)
-afraid to not be down to earth person, also to not be realistic or to have a certain logic
-afraid sewers (related to the point 1 and 2)
-afraid to fall in love
and well, overall what im afraid is "me falling"
Failing in studying , Cruz that is the only thing for me (a complete loner )
Dying with regrets ....
Regrets and fucking regretting , and dying with "what its"
What ifs
Being alone although I'm alone
Regrets including my future
Personally, my number one fear is being left alone. I will wake up and suddenly figure out that everyone around me could die, leave me, or just hate me. I deal with it by reading (both books and manga) because reading makes me feel less alone. Plus I also stay up that way my family doesn't die due to being surprised by someone entering our house when no one is awake. Both of these things help me think either I won't be alone due to already having eternal friends (Literature characters) or I can protect my family to make sure I am not alone and they don't die (though I would die if facing a murderer).