When do you know its love? Is this it or just a crush?

I dream about her and we don't have sex, we talk and act like a couple, kiss, do useless sh-t like watching movies or listening to music together, when I wake up is when I realize how stupid and idiotic I am of thinking about a girl who already said she isnt interested in me to a friend of hers. I try to ignore her, but I can't. She stares at me in school alot though. We are both seniors. Barely talked. She found out through a friend and said she isnt interested. Now I feel f-cked up and sometimes drink to try and feel better (Im 17) I know its not the right thing to do but it just takes the edge off. Is this love? It feels like hell btw. But I just cant get her outta my mind, I havent even masturbated since she rejected me, I just can't look at another girl in a romantic or hot way ever since I saw her, and I dont consider her hot, I consider her gorgeous and probably the biggest thing that attracted me was her smile, shes not even popular, shes shy as f-ck, only keeps to her friends and never dated anyone (niether have I, but I'm ugly as sh-t so I can be excused :P) We are both seniors in high school. Is this it? or just a crush?