Reddit, is it normal for a 17 year old to have a fake relationship in his head for almost 2 years?

It's pretty bad, I think about having a relationship with this girl at my school every time when I am alone. It is not like I have an altar of her or anything, it's just that I fantasize about having a relationship with her all the time. She's also a good friend of mine who has a boyfriend. it's driving me insane sometimes. Is this normal for someone my age? I think it's just a puberty thing but I don't know.

Thanks in advance.