Is it normal to feel people in my life are just existing in my own head

If I get too close with someone such as hanging out often or so I feel like they arent real. I feel my former best friend is like a part of me that when the friendship fell apart I lost and the times we have reconnected it hasnt been the same and its made me depressed. Like part of my head.
The guy im going out with now I can be myself with. The rare times I meet someone im honest and fully myself with I lost them in the graininess.
They dont feel like real existing people. He could just as well be someone I imagined. I know he isnt because of all the proof but whats telling me im not like Leonardo DiCaprio in Shutter Island or something? I could be and have no idea y'know. The few times I feel I can talk to somebody and sense a human connection to them I always end up suspecting on some level they are not real. At least the thought crosses my mind that what if i've been sitting talking to this person in public when in reality people have watched me talking to myself like a retard? I am convinced that people stare at me when im outside and if ive previously been seen conversating with non-existing people then that really are and it makes sense. The only person I ever feel comfortable with is myself so if I feel comfortable with somebody else then that is too suspicious. For all I know my brain is playing tricks on me and my family goes along with it to help me. Im sure that happens.
Haha, this reminds me of when I thought people could read my mind when I was a teen lol. Sometimes i'd think real nasty things about a bitch and right after I was done she'd turn to me and give me a mean stare. I still watch what I think around others to this day... Just yesterday I was thinking about asking my date about halloween but changed my mind and merely 2 seconds later he asked me about it instead. That has happened to me with other people as well. Kind of sus if you ask me. For all I know all of this is a simulation and no one around me exists. I think about that sometimes but not for long, it could be dangerous y'know... You lose your grip on what is considered sanity in this dimension and then you're fucked lol.