How to move on from my crush?

I am 20(M) How to move on from my crush ? Like she even don’t know I love her but, it feels like I should be loyal to her. I mean whenever I see some girls I immediately remember her and started feeling like she is my gf and I shouldn’t cheat her by looking at other girl. But infact I am nothing to her. Is this happen to everyone or just me? How to solve this issue?