[2] recent mental experiences (need help.. ?)

im not sure how to exactly start this, but i know i wanted to write about this for a while now.

ive been experiencing these weird out-of-person periods recently, as well as either hallucinating or just my mind playing really cruel tricks on me.

lets start with this fact- most of the time, i dont feel like a person. i feel like im stuck in someone's body, watching their choices, but that only started recently, and im not sure why. its been getting more and more intense lately, to the point where i barely get moments of 'me', but it doesnt fully feel like me either. its not like i dont have control of what i do, its that my body acts before my mind can fully realize what im going to do, and its driving me insane. it can go on for hours on end, it happens mostly when im around other people, but it happens when im alone, too.

i get heavy mood swings, i feel like i should mention that. not because of any specific reason; im not on my period or pregnant or anything like that, so no. one second im happy to do something, then cry about it, get angry, all in the time span of 5 minutes. im either excessively calm and silent, or excessively hyper and loud. it all depends on my surroundings and the people, but that can change too. 

im not sure what i am at this point. one second i know im myself, the second i dont. its like im playing a first person game on auto, letting cutscenes pass, while the only thing i can do is walking or minor activities. things i do before thinking range from good and actually healthy, to damaging. this state made me go out for walks, made me learn how to cook things, socialise, but it also made me harm myself, starve, and shut myself out.

to the hallucinations, theyre very specific, and only happen at certain times. whenever the room is slightly dark, has a dark spot or corner, im almost certain to see something there if i ever notice it. even if i dont notice the place at first, it haunts me. its always a sort of humanoid, tall with long limbs. they usually blend in with the color of darkness in the corner, with a contrasting color somewhere on its body. my description is not the best, but its what my mind captured; usually, I only see them for a split second, a sort of jumpscare. i walk into a room, see a clear sight of a disfigured creature, blink in fear, and its gone. i thought it was my mind just playing tricks on me, but im not sure anymore. its been happening way too frequently, and the creatures are getting clearer and clearer every time. surprisingly, it only happens when im alone in the room. if there is someone else, nothing will haunt me.

i will reread this later and hopefully add on more useful information, but id love to know what people think. is this normal? does everyone experience this and i just dont know it? if it helps, im sixteen and afab girl. its been digging into my head too much lately, and im not sure how much of this i can handle. i appreciate any kind of help.