What is wrong with me? Why do you always see secondary people?

Actually, everyone has the same experience as you. Everyone feels that a scene happened at some time a long time ago ... in fact, as you said, we live in a three-dimensional world. The two-dimensional world is actually a past era. In fact, everyone who comes into this world is doomed to die. Because they died in a two-dimensional world, they came to live in a three-dimensional world once.

After talking so much nonsense, my advice to you is: this kind of thing is mysterious, and it is useless to go to the hospital. So you should go to a folk fortune teller.