It’s been 6 years, 3 of which was falling in love with my fiancee, since we dated. It didn’t end poorly, and she was my first love. I can’t learn how to not think about her. She constantly appears in dreams and randomly pops up in mind when/ if I see red hair. I love my fiancee, she’s my better half and couldn’t be a better person or future mother.
It doesn’t change my random thoughts though and they’re starting to be painful. I should’ve told my fiancee about these thoughts long ago but now it’ll destroy her. I’m really not sure what’s going on in my head about it all. I want so bad to commit to my future but I literally cannot stop thoughts of a relationship from high school over 6 years ago. Do I just carry this forever?
LemonVibe 
You are not ready to marry. Your dream girl is human too but you are using her as a form of escapism. If you got her all you would do is dream of the greener pasture of your soon to be former fience. You should tell her and let her move on with her life however. Don’t waste her time to find a man who loves her and only her.