Feeling like I'm going crazy

I feel like im going crazy sometimes😶 i cant tell whats reality & whats a dream i dont know if its my lack of sleeping or cause i practically live inside my head making up scenarios of things that could of been. Like one time i was babysitting my Niece she was in the bedroom asleep with the light off & i was in the living room watching tv, from where i was i had a perfect view of her door which was half way open & suddenly i decided to just look over & when i focused my eyes in the pitch black room i clearly saw a black figure with long hair & long fingers/nails & i knew i didnt just imagined it because it wasn't like i saw it for a couple of seconds & i wasn't scared i was just shocked thinking was i being pranked but when i saw it sliding back i nearly just sat there for about 5 mins & when i remembered my niece was in there i ran in there & nobody was there with her & no places someone could of hide. since that day i believed it was a shadow person cause my brother & i been experiencing strange things i believe that day something followed me home.