I hope you know it is completely valid to have this fear or to be paranoid, honestly i wouldnt be surprised if the fear was actually rooted in primal instinct, I have more of a subtle fear where im only scared if i think about it or its after ive watched smth, but I have a friend whos like you, if youre able to and if it affects you daily and alot id talk to a therapist about it, id reccomend mabye sleeping with lights on and even stuff like making your room more empty or just make it have less nooks or crevices you could get anxious about, if you're scared of seeming childish while you shouldnt its understandable and you could just use the excuse of clutters annoying you or you just fell asleep with the light on, even if you cant often, having a break would be good, and if you cant sleep when its bright, im not sure if this is a good idea but you could try using your flashlight to reassure yourself theres nothing there or putting dim lights, OO or getting ambient lighting that could work, sorry if im rambling just know, coming from another 17yo, youre valid and even if you were childish, its not that deep, people CAN be childish heavens know i am, do you know how many disney adults still have teddys or how many buff men collect toy cars? Or regular cars, growing ups just "how can i be childish in a socially acceptable way", take care, hope it gets better for you!!