When you think that someone loves you or you may have imagined some famous celebrity falling in love with you at some point or you think that someone in high school has crushed you but it is not really called erotomania.
This could be a person you have never met. He may even be a famous person. You can be so sure of this love that you feel like you are in a relationship with this person.
Erotomania is a type of delusion. In psychology these are defined as convictions that do not change.
Erotomania has been cited as a symptom of dementia. Dementia can have many themes of confusion.
In the case of erotomania, the illusion is usually presented as a fixation on someone with a belief that they have fallen in love with you. But not at all.