I don’t know in which subreddit I should be posting this so if it’s a little out of topic I’m sorry.

So... recently I’ve been looking back on my past. I was seeing photos of me and my friends and I don’t remember taking the photos. I did not even remember when and where it was. Some other events I do know where and when it happened, but I can’t remember it happening. 
I have a lot of deja vu. Everywhere I go I have the feeling that I have already been there, knowing that I haven’t. 
I’ve always felt random pains on my hands, arms, legs and head. It never lasts more than 2 minutes, and they are very random, but more often at night. 
I’ve always experienced delusional thoughts.
Whenever I’m talking to my friends, it looks like I’m not really there at that moment, and that my mind is somewhere else.
I see flashes of flight.
Sometimes everything goes dark for a second.
Sometimes I can’t understand what people are saying (both in my native language and in English - sometimes they might even sound like I don’t know them) 
Every time I search for something about health I get dizzy/headache. If I think a little bit more than normal (especially about me) I also feel dizzy/get a headache.

Is this serious? What can this be? Who should I talk to?