I Am Confused About My Relationship

So a few days ago.I started a relationship with this amazing girl on here.I really like her but I messed up.

I fall fast and hard for people once I start caring for someone it is to the max.But I told her that I love her.

She then blew up at me.Telling me that I don't really like her.I really like her and my feelings are strong.But she is probably right.But I'm scared I'm loosing her.This is my first legit relationship.And I know I messed up with this.i guess I was living in that fantasy I always had when I'm in a relationship with a girl I tell her that I love her and she loves me to.I want to be able for the both of us to really for me and her to be in love.How can I fix this?I don't want to loose her.